diff --git a/CHANGELOG.md b/CHANGELOG.md
index 12b595933..9883c3dd7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 ### Added
 
 - Xlsx Reader Optionally Ignore Rows With No Cells. [Issue #3982](https://github.com/PHPOffice/PhpSpreadsheet/issues/3982) [PR #4035](https://github.com/PHPOffice/PhpSpreadsheet/pull/4035)
+- Means to change style without affecting current cell/sheet. [PR #4073](https://github.com/PHPOffice/PhpSpreadsheet/pull/4073)
 - Option for CSV output file to have varying numbers of columns for each row. [Issue #1415](https://github.com/PHPOffice/PhpSpreadsheet/issues/1415) [PR #4076](https://github.com/PHPOffice/PhpSpreadsheet/pull/4076)
 
 ### Changed
@@ -34,10 +35,13 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 - Mpdf and Tcpdf Borders on Merged Cells. [Issue #3557](https://github.com/PHPOffice/PhpSpreadsheet/issues/3557) [PR #4047](https://github.com/PHPOffice/PhpSpreadsheet/pull/4047)
 - Xls Conditional Format Improvements. [PR #4030](https://github.com/PHPOffice/PhpSpreadsheet/pull/4030) [PR #4033](https://github.com/PHPOffice/PhpSpreadsheet/pull/4033)
 - Conditional Range Unions and Intersections [Issue #4039](https://github.com/PHPOffice/PhpSpreadsheet/issues/4039) [PR #4042](https://github.com/PHPOffice/PhpSpreadsheet/pull/4042)
+- Ods comments with newlines. [Issue #4081](https://github.com/PHPOffice/PhpSpreadsheet/issues/4081) [PR #4086](https://github.com/PHPOffice/PhpSpreadsheet/pull/4086)
+- Propagate errors in Text functions. [Issue #2581](https://github.com/PHPOffice/PhpSpreadsheet/issues/2581) [PR #4080](https://github.com/PHPOffice/PhpSpreadsheet/pull/4080)
 - Csv Reader allow use of html mimetype. [Issue #4036](https://github.com/PHPOffice/PhpSpreadsheet/issues/4036) [PR #4040](https://github.com/PHPOffice/PhpSpreadsheet/pull/4040)
 - Problem rendering line chart with missing plot label. [PR #4074](https://github.com/PHPOffice/PhpSpreadsheet/pull/4074)
 - More RTL in Xlsx/Html Comments [Issue #4004](https://github.com/PHPOffice/PhpSpreadsheet/issues/4004) [PR #4065](https://github.com/PHPOffice/PhpSpreadsheet/pull/4065)
 - Empty String in sharedStrings. [Issue #4063](https://github.com/PHPOffice/PhpSpreadsheet/issues/4063) [PR #4064](https://github.com/PHPOffice/PhpSpreadsheet/pull/4064)
+- Treat invalid formulas as strings. [Issue #1310](https://github.com/PHPOffice/PhpSpreadsheet/issues/1310) [PR #4073](https://github.com/PHPOffice/PhpSpreadsheet/pull/4073)
 
 ## 2024-05-11 - 2.1.0
 
diff --git a/src/PhpSpreadsheet/Calculation/Calculation.php b/src/PhpSpreadsheet/Calculation/Calculation.php
index 257d1d06c..2b8a7bc65 100644
--- a/src/PhpSpreadsheet/Calculation/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation/Calculation.php
@@ -4082,7 +4082,7 @@ class Calculation
             $opCharacter = $formula[$index]; //    Get the first character of the value at the current index position
 
             // Check for two-character operators (e.g. >=, <=, <>)
-            if ((isset(self::$comparisonOperators[$opCharacter])) && (strlen($formula) > $index) && (isset(self::$comparisonOperators[$formula[$index + 1]]))) {
+            if ((isset(self::$comparisonOperators[$opCharacter])) && (strlen($formula) > $index) && isset($formula[$index + 1], self::$comparisonOperators[$formula[$index + 1]])) {
                 $opCharacter .= $formula[++$index];
             }
             //    Find out if we're currently at the beginning of a number, variable, cell/row/column reference,
@@ -4810,13 +4810,20 @@ class Calculation
 
                             for ($row = 0; $row < $rows; ++$row) {
                                 for ($column = 0; $column < $columns; ++$column) {
-                                    $operand1[$row][$column]
-                                        = Shared\StringHelper::substring(
-                                            self::boolToString($operand1[$row][$column])
-                                            . self::boolToString($operand2[$row][$column]),
-                                            0,
-                                            DataType::MAX_STRING_LENGTH
-                                        );
+                                    $op1x = self::boolToString($operand1[$row][$column]);
+                                    $op2x = self::boolToString($operand2[$row][$column]);
+                                    if (Information\ErrorValue::isError($op1x)) {
+                                        // no need to do anything
+                                    } elseif (Information\ErrorValue::isError($op2x)) {
+                                        $operand1[$row][$column] = $op2x;
+                                    } else {
+                                        $operand1[$row][$column]
+                                            = Shared\StringHelper::substring(
+                                                $op1x . $op2x,
+                                                0,
+                                                DataType::MAX_STRING_LENGTH
+                                            );
+                                    }
                                 }
                             }
                             $result = $operand1;
@@ -4826,7 +4833,13 @@ class Calculation
                             // using the concatenation operator
                             // with literals that fits in 32K,
                             // so I don't think we can overflow here.
-                            $result = self::FORMULA_STRING_QUOTE . str_replace('""', self::FORMULA_STRING_QUOTE, self::unwrapResult($operand1) . self::unwrapResult($operand2)) . self::FORMULA_STRING_QUOTE;
+                            if (Information\ErrorValue::isError($operand1)) {
+                                $result = $operand1;
+                            } elseif (Information\ErrorValue::isError($operand2)) {
+                                $result = $operand2;
+                            } else {
+                                $result = self::FORMULA_STRING_QUOTE . str_replace('""', self::FORMULA_STRING_QUOTE, self::unwrapResult($operand1) . self::unwrapResult($operand2)) . self::FORMULA_STRING_QUOTE;
+                            }
                         }
                         $this->debugLog->writeDebugLog('Evaluation Result is %s', $this->showTypeDetails($result));
                         $stack->push('Value', $result);
diff --git a/src/PhpSpreadsheet/Calculation/Functions.php b/src/PhpSpreadsheet/Calculation/Functions.php
index 6b7450069..77f8317ae 100644
--- a/src/PhpSpreadsheet/Calculation/Functions.php
+++ b/src/PhpSpreadsheet/Calculation/Functions.php
@@ -26,6 +26,8 @@ class Functions
     const RETURNDATE_PHP_DATETIME_OBJECT = 'O';
     const RETURNDATE_EXCEL = 'E';
 
+    public const NOT_YET_IMPLEMENTED = '#Not Yet Implemented';
+
     /**
      * Compatibility mode to use for error checking and responses.
      */
@@ -123,7 +125,7 @@ class Functions
      */
     public static function DUMMY(): string
     {
-        return '#Not Yet Implemented';
+        return self::NOT_YET_IMPLEMENTED;
     }
 
     public static function isMatrixValue(mixed $idx): bool
diff --git a/src/PhpSpreadsheet/Calculation/Information/ErrorValue.php b/src/PhpSpreadsheet/Calculation/Information/ErrorValue.php
index dcef43990..f3a746273 100644
--- a/src/PhpSpreadsheet/Calculation/Information/ErrorValue.php
+++ b/src/PhpSpreadsheet/Calculation/Information/ErrorValue.php
@@ -3,6 +3,7 @@
 namespace PhpOffice\PhpSpreadsheet\Calculation\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 
 class ErrorValue
 {
@@ -35,7 +36,7 @@ class ErrorValue
      * @return array|bool If an array of numbers is passed as an argument, then the returned result will also be an array
      *            with the same dimensions
      */
-    public static function isError(mixed $value = ''): array|bool
+    public static function isError(mixed $value = '', bool $tryNotImplemented = false): array|bool
     {
         if (is_array($value)) {
             return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $value);
@@ -44,6 +45,9 @@ class ErrorValue
         if (!is_string($value)) {
             return false;
         }
+        if ($tryNotImplemented && $value === Functions::NOT_YET_IMPLEMENTED) {
+            return true;
+        }
 
         return in_array($value, ExcelError::ERROR_CODES, true);
     }
diff --git a/src/PhpSpreadsheet/Calculation/TextData/CaseConvert.php b/src/PhpSpreadsheet/Calculation/TextData/CaseConvert.php
index 83cc4ee1f..6667bac54 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/CaseConvert.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/CaseConvert.php
@@ -3,6 +3,7 @@
 namespace PhpOffice\PhpSpreadsheet\Calculation\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcExp;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 
 class CaseConvert
@@ -26,7 +27,11 @@ class CaseConvert
             return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $mixedCaseValue);
         }
 
-        $mixedCaseValue = Helpers::extractString($mixedCaseValue);
+        try {
+            $mixedCaseValue = Helpers::extractString($mixedCaseValue, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
 
         return StringHelper::strToLower($mixedCaseValue);
     }
@@ -48,7 +53,11 @@ class CaseConvert
             return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $mixedCaseValue);
         }
 
-        $mixedCaseValue = Helpers::extractString($mixedCaseValue);
+        try {
+            $mixedCaseValue = Helpers::extractString($mixedCaseValue, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
 
         return StringHelper::strToUpper($mixedCaseValue);
     }
@@ -70,7 +79,11 @@ class CaseConvert
             return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $mixedCaseValue);
         }
 
-        $mixedCaseValue = Helpers::extractString($mixedCaseValue);
+        try {
+            $mixedCaseValue = Helpers::extractString($mixedCaseValue, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
 
         return StringHelper::strToTitle($mixedCaseValue);
     }
diff --git a/src/PhpSpreadsheet/Calculation/TextData/CharacterConvert.php b/src/PhpSpreadsheet/Calculation/TextData/CharacterConvert.php
index 8d90a17ba..06d0f9009 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/CharacterConvert.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/CharacterConvert.php
@@ -3,6 +3,7 @@
 namespace PhpOffice\PhpSpreadsheet\Calculation\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcExp;
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
@@ -26,7 +27,12 @@ class CharacterConvert
             return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $character);
         }
 
-        $character = Helpers::validateInt($character);
+        try {
+            $character = Helpers::validateInt($character, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
+
         $min = Functions::getCompatibilityMode() === Functions::COMPATIBILITY_OPENOFFICE ? 0 : 1;
         if ($character < $min || $character > 255) {
             return ExcelError::VALUE();
@@ -52,7 +58,12 @@ class CharacterConvert
             return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $characters);
         }
 
-        $characters = Helpers::extractString($characters);
+        try {
+            $characters = Helpers::extractString($characters, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
+
         if ($characters === '') {
             return ExcelError::VALUE();
         }
diff --git a/src/PhpSpreadsheet/Calculation/TextData/Concatenate.php b/src/PhpSpreadsheet/Calculation/TextData/Concatenate.php
index 62e9c3895..337a64a60 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/Concatenate.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/Concatenate.php
@@ -28,7 +28,7 @@ class Concatenate
 
         foreach ($aArgs as $arg) {
             $value = Helpers::extractString($arg);
-            if (ErrorValue::isError($value)) {
+            if (ErrorValue::isError($value, true)) {
                 $returnValue = $value;
 
                 break;
@@ -140,7 +140,7 @@ class Concatenate
     {
         foreach ($aArgs as $key => &$arg) {
             $value = Helpers::extractString($arg);
-            if (ErrorValue::isError($value)) {
+            if (ErrorValue::isError($value, true)) {
                 return $value;
             }
 
@@ -178,7 +178,7 @@ class Concatenate
 
         if (!is_numeric($repeatCount) || $repeatCount < 0) {
             $returnValue = ExcelError::VALUE();
-        } elseif (ErrorValue::isError($stringValue)) {
+        } elseif (ErrorValue::isError($stringValue, true)) {
             $returnValue = $stringValue;
         } else {
             $returnValue = str_repeat($stringValue, (int) $repeatCount);
diff --git a/src/PhpSpreadsheet/Calculation/TextData/Extract.php b/src/PhpSpreadsheet/Calculation/TextData/Extract.php
index 32e5b967a..1dfb724cd 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/Extract.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/Extract.php
@@ -31,7 +31,7 @@ class Extract
         }
 
         try {
-            $value = Helpers::extractString($value);
+            $value = Helpers::extractString($value, true);
             $chars = Helpers::extractInt($chars, 0, 1);
         } catch (CalcExp $e) {
             return $e->getMessage();
@@ -61,7 +61,7 @@ class Extract
         }
 
         try {
-            $value = Helpers::extractString($value);
+            $value = Helpers::extractString($value, true);
             $start = Helpers::extractInt($start, 1);
             $chars = Helpers::extractInt($chars, 0);
         } catch (CalcExp $e) {
@@ -90,7 +90,7 @@ class Extract
         }
 
         try {
-            $value = Helpers::extractString($value);
+            $value = Helpers::extractString($value, true);
             $chars = Helpers::extractInt($chars, 0, 1);
         } catch (CalcExp $e) {
             return $e->getMessage();
@@ -132,7 +132,13 @@ class Extract
             return self::evaluateArrayArgumentsIgnore([self::class, __FUNCTION__], 1, $text, $delimiter, $instance, $matchMode, $matchEnd, $ifNotFound);
         }
 
-        $text = Helpers::extractString($text ?? '');
+        try {
+            $text = Helpers::extractString($text ?? '', true);
+            Helpers::extractString(Functions::flattenSingleValue($delimiter ?? ''), true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
+
         $instance = (int) $instance;
         $matchMode = (int) $matchMode;
         $matchEnd = (int) $matchEnd;
@@ -190,7 +196,13 @@ class Extract
             return self::evaluateArrayArgumentsIgnore([self::class, __FUNCTION__], 1, $text, $delimiter, $instance, $matchMode, $matchEnd, $ifNotFound);
         }
 
-        $text = Helpers::extractString($text ?? '');
+        try {
+            $text = Helpers::extractString($text ?? '', true);
+            Helpers::extractString(Functions::flattenSingleValue($delimiter ?? ''), true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
+
         $instance = (int) $instance;
         $matchMode = (int) $matchMode;
         $matchEnd = (int) $matchEnd;
diff --git a/src/PhpSpreadsheet/Calculation/TextData/Format.php b/src/PhpSpreadsheet/Calculation/TextData/Format.php
index 40335ced7..0560b376b 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/Format.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/Format.php
@@ -8,6 +8,7 @@ use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
 use PhpOffice\PhpSpreadsheet\Calculation\DateTimeExcel;
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcExp;
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PhpOffice\PhpSpreadsheet\Calculation\Information\ErrorValue;
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 use PhpOffice\PhpSpreadsheet\Calculation\MathTrig;
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
@@ -123,8 +124,13 @@ class Format
             return self::evaluateArrayArguments([self::class, __FUNCTION__], $value, $format);
         }
 
-        $value = Helpers::extractString($value);
-        $format = Helpers::extractString($format);
+        try {
+            $value = Helpers::extractString($value, true);
+            $format = Helpers::extractString($format, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
+
         $format = (string) NumberFormat::convertSystemFormats($format);
 
         if (!is_numeric($value) && Date::isDateTimeFormatCode($format)) {
@@ -152,6 +158,9 @@ class Format
         }
         if (is_string($value)) {
             $value = trim($value);
+            if (ErrorValue::isError($value, true)) {
+                throw new CalcExp($value);
+            }
             if ($spacesMeanZero && $value === '') {
                 $value = 0;
             }
@@ -220,7 +229,7 @@ class Format
     }
 
     /**
-     * TEXT.
+     * VALUETOTEXT.
      *
      * @param mixed $value The value to format
      *                         Or can be an array of values
diff --git a/src/PhpSpreadsheet/Calculation/TextData/Helpers.php b/src/PhpSpreadsheet/Calculation/TextData/Helpers.php
index 15b046704..719de04a8 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/Helpers.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/Helpers.php
@@ -27,7 +27,7 @@ class Helpers
         if (is_bool($value)) {
             return self::convertBooleanValue($value);
         }
-        if ($throwIfError && is_string($value) && ErrorValue::isError($value)) {
+        if ($throwIfError && is_string($value) && ErrorValue::isError($value, true)) {
             throw new CalcExp($value);
         }
 
@@ -63,18 +63,28 @@ class Helpers
             $value = (float) $value;
         }
         if (!is_numeric($value)) {
+            if (is_string($value) && ErrorValue::isError($value, true)) {
+                throw new CalcExp($value);
+            }
+
             throw new CalcExp(ExcelError::VALUE());
         }
 
         return (float) $value;
     }
 
-    public static function validateInt(mixed $value): int
+    public static function validateInt(mixed $value, bool $throwIfError = false): int
     {
         if ($value === null) {
             $value = 0;
         } elseif (is_bool($value)) {
             $value = (int) $value;
+        } elseif ($throwIfError && is_string($value) && !is_numeric($value)) {
+            if (!ErrorValue::isError($value, true)) {
+                $value = ExcelError::VALUE();
+            }
+
+            throw new CalcExp($value);
         }
 
         return (int) $value;
diff --git a/src/PhpSpreadsheet/Calculation/TextData/Search.php b/src/PhpSpreadsheet/Calculation/TextData/Search.php
index ad83f1a37..663d49fc2 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/Search.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/Search.php
@@ -32,8 +32,8 @@ class Search
         }
 
         try {
-            $needle = Helpers::extractString($needle);
-            $haystack = Helpers::extractString($haystack);
+            $needle = Helpers::extractString($needle, true);
+            $haystack = Helpers::extractString($haystack, true);
             $offset = Helpers::extractInt($offset, 1, 0, true);
         } catch (CalcExp $e) {
             return $e->getMessage();
@@ -74,8 +74,8 @@ class Search
         }
 
         try {
-            $needle = Helpers::extractString($needle);
-            $haystack = Helpers::extractString($haystack);
+            $needle = Helpers::extractString($needle, true);
+            $haystack = Helpers::extractString($haystack, true);
             $offset = Helpers::extractInt($offset, 1, 0, true);
         } catch (CalcExp $e) {
             return $e->getMessage();
diff --git a/src/PhpSpreadsheet/Calculation/TextData/Text.php b/src/PhpSpreadsheet/Calculation/TextData/Text.php
index 44e0cd402..f988a6c19 100644
--- a/src/PhpSpreadsheet/Calculation/TextData/Text.php
+++ b/src/PhpSpreadsheet/Calculation/TextData/Text.php
@@ -4,6 +4,7 @@ namespace PhpOffice\PhpSpreadsheet\Calculation\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcExp;
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ErrorValue;
 
@@ -17,16 +18,20 @@ class Text
      * @param mixed $value String Value
      *                         Or can be an array of values
      *
-     * @return array|int If an array of values is passed for the argument, then the returned result
+     * @return array|int|string If an array of values is passed for the argument, then the returned result
      *            will also be an array with matching dimensions
      */
-    public static function length(mixed $value = ''): array|int
+    public static function length(mixed $value = ''): array|int|string
     {
         if (is_array($value)) {
             return self::evaluateSingleArgumentArray([self::class, __FUNCTION__], $value);
         }
 
-        $value = Helpers::extractString($value);
+        try {
+            $value = Helpers::extractString($value, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
 
         return mb_strlen($value, 'UTF-8');
     }
@@ -41,17 +46,21 @@ class Text
      * @param mixed $value2 String Value
      *                         Or can be an array of values
      *
-     * @return array|bool If an array of values is passed for either of the arguments, then the returned result
+     * @return array|bool|string If an array of values is passed for either of the arguments, then the returned result
      *            will also be an array with matching dimensions
      */
-    public static function exact(mixed $value1, mixed $value2): array|bool
+    public static function exact(mixed $value1, mixed $value2): array|bool|string
     {
         if (is_array($value1) || is_array($value2)) {
             return self::evaluateArrayArguments([self::class, __FUNCTION__], $value1, $value2);
         }
 
-        $value1 = Helpers::extractString($value1);
-        $value2 = Helpers::extractString($value2);
+        try {
+            $value1 = Helpers::extractString($value1, true);
+            $value2 = Helpers::extractString($value2, true);
+        } catch (CalcExp $e) {
+            return $e->getMessage();
+        }
 
         return $value2 === $value1;
     }
@@ -97,11 +106,14 @@ class Text
      * @param mixed $padding The value with which to pad the result.
      *                              The default is #N/A.
      *
-     * @return array the array built from the text, split by the row and column delimiters
+     * @return array|string the array built from the text, split by the row and column delimiters, or an error string
      */
-    public static function split(mixed $text, $columnDelimiter = null, $rowDelimiter = null, bool $ignoreEmpty = false, bool $matchMode = true, mixed $padding = '#N/A'): array
+    public static function split(mixed $text, $columnDelimiter = null, $rowDelimiter = null, bool $ignoreEmpty = false, bool $matchMode = true, mixed $padding = '#N/A'): array|string
     {
         $text = Functions::flattenSingleValue($text);
+        if (ErrorValue::isError($text, true)) {
+            return $text;
+        }
 
         $flags = self::matchFlags($matchMode);
 
diff --git a/src/PhpSpreadsheet/Cell/Cell.php b/src/PhpSpreadsheet/Cell/Cell.php
index e205b73ee..29649405a 100644
--- a/src/PhpSpreadsheet/Cell/Cell.php
+++ b/src/PhpSpreadsheet/Cell/Cell.php
@@ -4,6 +4,7 @@ namespace PhpOffice\PhpSpreadsheet\Cell;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalculationException;
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 use PhpOffice\PhpSpreadsheet\Collection\Cells;
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
@@ -257,6 +258,7 @@ class Cell implements Stringable
     public function setValueExplicit(mixed $value, string $dataType = DataType::TYPE_STRING): self
     {
         $oldValue = $this->value;
+        $quotePrefix = false;
 
         // set the value according to data type
         switch ($dataType) {
@@ -269,6 +271,10 @@ class Cell implements Stringable
                 // no break
             case DataType::TYPE_STRING:
                 // Synonym for string
+                if (is_string($value) && strlen($value) > 1 && $value[0] === '=') {
+                    $quotePrefix = true;
+                }
+                // no break
             case DataType::TYPE_INLINE:
                 // Rich text
                 if ($value !== null && !is_scalar($value) && !($value instanceof Stringable)) {
@@ -314,6 +320,7 @@ class Cell implements Stringable
         $this->updateInCollection();
         $cellCoordinate = $this->getCoordinate();
         self::updateIfCellIsTableHeader($this->getParent()?->getParent(), $this, $oldValue, $value);
+        $this->getWorksheet()->applyStylesFromArray($cellCoordinate, ['quotePrefix' => $quotePrefix]);
 
         return $this->getParent()?->get($cellCoordinate) ?? $this;
     }
@@ -536,7 +543,7 @@ class Cell implements Stringable
             }
             SharedDate::setExcelCalendar($currentCalendar);
 
-            if ($result === '#Not Yet Implemented') {
+            if ($result === Functions::NOT_YET_IMPLEMENTED) {
                 return $this->calculatedValue; // Fallback if calculation engine does not support the formula.
             }
 
diff --git a/src/PhpSpreadsheet/Cell/DefaultValueBinder.php b/src/PhpSpreadsheet/Cell/DefaultValueBinder.php
index 6f75a90a8..f36934ed3 100644
--- a/src/PhpSpreadsheet/Cell/DefaultValueBinder.php
+++ b/src/PhpSpreadsheet/Cell/DefaultValueBinder.php
@@ -3,6 +3,8 @@
 namespace PhpOffice\PhpSpreadsheet\Cell;
 
 use DateTimeInterface;
+use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalculationException;
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
@@ -68,6 +70,23 @@ class DefaultValueBinder implements IValueBinder
             throw new SpreadsheetException("unusable type $gettype");
         }
         if (strlen($value) > 1 && $value[0] === '=') {
+            $calculation = new Calculation();
+            $calculation->disableBranchPruning();
+
+            try {
+                if (empty($calculation->parseFormula($value))) {
+                    return DataType::TYPE_STRING;
+                }
+            } catch (CalculationException $e) {
+                $message = $e->getMessage();
+                if (
+                    $message === 'Formula Error: An unexpected error occurred'
+                    || str_contains($message, 'has no operands')
+                ) {
+                    return DataType::TYPE_STRING;
+                }
+            }
+
             return DataType::TYPE_FORMULA;
         }
         if (preg_match('/^[\+\-]?(\d+\\.?\d*|\d*\\.?\d+)([Ee][\-\+]?[0-2]?\d{1,3})?$/', $value)) {
diff --git a/src/PhpSpreadsheet/Cell/StringValueBinder.php b/src/PhpSpreadsheet/Cell/StringValueBinder.php
index 6ff258d93..d86cdabd3 100644
--- a/src/PhpSpreadsheet/Cell/StringValueBinder.php
+++ b/src/PhpSpreadsheet/Cell/StringValueBinder.php
@@ -8,7 +8,7 @@ use PhpOffice\PhpSpreadsheet\RichText\RichText;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 use Stringable;
 
-class StringValueBinder implements IValueBinder
+class StringValueBinder extends DefaultValueBinder implements IValueBinder
 {
     protected bool $convertNull = true;
 
@@ -87,12 +87,9 @@ class StringValueBinder implements IValueBinder
             $cell->setValueExplicit($value, DataType::TYPE_BOOL);
         } elseif ((is_int($value) || is_float($value)) && $this->convertNumeric === false) {
             $cell->setValueExplicit($value, DataType::TYPE_NUMERIC);
-        } elseif (is_string($value) && strlen($value) > 1 && $value[0] === '=' && $this->convertFormula === false) {
+        } elseif (is_string($value) && strlen($value) > 1 && $value[0] === '=' && $this->convertFormula === false && parent::dataTypeForValue($value) === DataType::TYPE_FORMULA) {
             $cell->setValueExplicit($value, DataType::TYPE_FORMULA);
         } else {
-            if (is_string($value) && strlen($value) > 1 && $value[0] === '=') {
-                $cell->getStyle()->setQuotePrefix(true);
-            }
             $cell->setValueExplicit((string) $value, DataType::TYPE_STRING);
         }
 
diff --git a/src/PhpSpreadsheet/Reader/Ods.php b/src/PhpSpreadsheet/Reader/Ods.php
index 2214369bc..0eefc8452 100644
--- a/src/PhpSpreadsheet/Reader/Ods.php
+++ b/src/PhpSpreadsheet/Reader/Ods.php
@@ -452,14 +452,25 @@ class Ods extends BaseReader
 
                                 if ($annotation->length > 0 && $annotation->item(0) !== null) {
                                     $textNode = $annotation->item(0)->getElementsByTagNameNS($textNs, 'p');
+                                    $textNodeLength = $textNode->length;
+                                    $newLineOwed = false;
+                                    for ($textNodeIndex = 0; $textNodeIndex < $textNodeLength; ++$textNodeIndex) {
+                                        $textNodeItem = $textNode->item($textNodeIndex);
+                                        if ($textNodeItem !== null) {
+                                            $text = $this->scanElementForText($textNodeItem);
+                                            if ($newLineOwed) {
+                                                $spreadsheet->getActiveSheet()
+                                                    ->getComment($columnID . $rowID)
+                                                    ->getText()
+                                                    ->createText("\n");
+                                            }
+                                            $newLineOwed = true;
 
-                                    if ($textNode->length > 0 && $textNode->item(0) !== null) {
-                                        $text = $this->scanElementForText($textNode->item(0));
-
-                                        $spreadsheet->getActiveSheet()
-                                            ->getComment($columnID . $rowID)
-                                            ->setText($this->parseRichText($text));
-//                                                                    ->setAuthor( $author )
+                                            $spreadsheet->getActiveSheet()
+                                                ->getComment($columnID . $rowID)
+                                                ->getText()
+                                                ->createText($this->parseRichText($text));
+                                        }
                                     }
                                 }
 
@@ -750,6 +761,8 @@ class Ods extends BaseReader
             /** @var DOMNode $child */
             if ($child->nodeType == XML_TEXT_NODE) {
                 $str .= $child->nodeValue;
+            } elseif ($child->nodeType == XML_ELEMENT_NODE && $child->nodeName == 'text:line-break') {
+                $str .= "\n";
             } elseif ($child->nodeType == XML_ELEMENT_NODE && $child->nodeName == 'text:s') {
                 // It's a space
 
diff --git a/src/PhpSpreadsheet/Worksheet/Worksheet.php b/src/PhpSpreadsheet/Worksheet/Worksheet.php
index 8119547d3..ae80cbc0b 100644
--- a/src/PhpSpreadsheet/Worksheet/Worksheet.php
+++ b/src/PhpSpreadsheet/Worksheet/Worksheet.php
@@ -3714,5 +3714,20 @@ class Worksheet implements IComparable
         }
 
         return false;
+    }      
+
+    public function applyStylesFromArray(string $coordinate, array $styleArray): bool
+    {
+        $spreadsheet = $this->parent;
+        if ($spreadsheet === null) {
+            return false;
+        }
+        $activeSheetIndex = $spreadsheet->getActiveSheetIndex();
+        $originalSelected = $this->selectedCells;
+        $this->getStyle($coordinate)->applyFromArray($styleArray);
+        $this->selectedCells = $originalSelected;
+        $spreadsheet->setActiveSheetIndex($activeSheetIndex);
+
+        return true;
     }
 }
diff --git a/src/PhpSpreadsheet/Writer/Ods/Cell/Comment.php b/src/PhpSpreadsheet/Writer/Ods/Cell/Comment.php
index b0829bf1d..f0b7d5704 100644
--- a/src/PhpSpreadsheet/Writer/Ods/Cell/Comment.php
+++ b/src/PhpSpreadsheet/Writer/Ods/Cell/Comment.php
@@ -24,7 +24,22 @@ class Comment
         $objWriter->writeAttribute('svg:x', $comment->getMarginLeft());
         $objWriter->writeAttribute('svg:y', $comment->getMarginTop());
         $objWriter->writeElement('dc:creator', $comment->getAuthor());
-        $objWriter->writeElement('text:p', $comment->getText()->getPlainText());
+
+        $objWriter->startElement('text:p');
+        $text = $comment->getText()->getPlainText();
+        $textElements = explode("\n", $text);
+        $newLineOwed = false;
+        foreach ($textElements as $textSegment) {
+            if ($newLineOwed) {
+                $objWriter->writeElement('text:line-break');
+            }
+            $newLineOwed = true;
+            if ($textSegment !== '') {
+                $objWriter->writeElement('text:span', $textSegment);
+            }
+        }
+        $objWriter->endElement(); // text:p
+
         $objWriter->endElement();
     }
 }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php b/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php
index fbac0ff91..aa7bc529d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php
@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Engine;
 
+use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 use PhpOffice\PhpSpreadsheet\NamedRange;
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
@@ -13,13 +14,23 @@ class RangeTest extends TestCase
 {
     private string $incompleteMessage = 'Must be revisited';
 
-    private Spreadsheet $spreadSheet;
+    private ?Spreadsheet $spreadSheet = null;
 
-    protected function setUp(): void
+    protected function getSpreadsheet(): Spreadsheet
     {
-        $this->spreadSheet = new Spreadsheet();
-        $this->spreadSheet->getActiveSheet()
+        $spreadsheet = new Spreadsheet();
+        $spreadsheet->getActiveSheet()
             ->fromArray(array_chunk(range(1, 240), 6), null, 'A1', true);
+
+        return $spreadsheet;
+    }
+
+    protected function tearDown(): void
+    {
+        if ($this->spreadSheet !== null) {
+            $this->spreadSheet->disconnectWorksheets();
+            $this->spreadSheet = null;
+        }
     }
 
     /**
@@ -27,6 +38,7 @@ class RangeTest extends TestCase
      */
     public function testRangeEvaluation(string $formula, int|string $expectedResult): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         $workSheet->setCellValue('H1', $formula);
 
@@ -64,8 +76,20 @@ class RangeTest extends TestCase
         ];
     }
 
+    public function test3dRangeParsing(): void
+    {
+        // This test shows that parsing throws exception.
+        // Next test shows that formula is still treated as a formula
+        //     despite the parse failure.
+        $this->expectExceptionMessage('3D Range references are not yet supported');
+        $calculation = new Calculation();
+        $calculation->disableBranchPruning();
+        $calculation->parseFormula('=SUM(Worksheet!A1:Worksheet2!B3');
+    }
+
     public function test3dRangeEvaluation(): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         $workSheet->setCellValue('E1', '=SUM(Worksheet!A1:Worksheet2!B3)');
 
@@ -78,6 +102,7 @@ class RangeTest extends TestCase
      */
     public function testNamedRangeEvaluation(array $ranges, string $formula, int $expectedResult): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         foreach ($ranges as $id => $range) {
             $this->spreadSheet->addNamedRange(new NamedRange('GROUP' . ++$id, $workSheet, $range));
@@ -116,6 +141,7 @@ class RangeTest extends TestCase
      */
     public function testUTF8NamedRangeEvaluation(array $names, array $ranges, string $formula, int $expectedResult): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         foreach ($names as $index => $name) {
             $range = $ranges[$index];
@@ -144,6 +170,7 @@ class RangeTest extends TestCase
         if ($this->incompleteMessage !== '') {
             self::markTestIncomplete($this->incompleteMessage);
         }
+        $this->spreadSheet = $this->getSpreadsheet();
 
         $workSheet = $this->spreadSheet->getActiveSheet();
         $this->spreadSheet->addNamedRange(new NamedRange('COMPOSITE', $workSheet, $composite));
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ErrorPropagationTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ErrorPropagationTest.php
new file mode 100644
index 000000000..9ab19d94c
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ErrorPropagationTest.php
@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
+
+class ErrorPropagationTest extends AllSetupTeardown
+{
+    public function testErrorPropagation(): void
+    {
+        $sheet = $this->getSheet();
+        $sheet->getCell('A1')->setValue('=ABS("X")');
+        self::assertSame('#VALUE!', $sheet->getCell('A1')->getCalculatedValue());
+        $sheet->getCell('A2')->setValue('=SQRT(-1)');
+        self::assertSame('#NUM!', $sheet->getCell('A2')->getCalculatedValue());
+        $sheet->getCell('A3')->setValue('=3/0');
+        self::assertSame('#DIV/0!', $sheet->getCell('A3')->getCalculatedValue());
+        $sheet->getCell('A4')->setValue('=XXXX()');
+        self::assertSame('#NAME?', $sheet->getCell('A4')->getCalculatedValue());
+        $sheet->getCell('A5')->setValue('=ABS("X")');
+        self::assertSame('#VALUE!', $sheet->getCell('A5')->getCalculatedValue());
+
+        $sheet->getCell('B1')->setValue('=UPPER(A1)');
+        self::assertSame('#VALUE!', $sheet->getCell('A1')->getCalculatedValue());
+        $sheet->getCell('B2')->setValue('=LOWER(A2)');
+        self::assertSame('#NUM!', $sheet->getCell('A2')->getCalculatedValue());
+        $sheet->getCell('B3')->setValue('=PROPER(A3)');
+        self::assertSame('#DIV/0!', $sheet->getCell('A3')->getCalculatedValue());
+
+        $sheet->getCell('C2')->setValue('=CHAR(A2)');
+        self::assertSame('#NUM!', $sheet->getCell('C2')->getCalculatedValue());
+        $sheet->getCell('C3')->setValue('=CODE(A3)');
+        self::assertSame('#DIV/0!', $sheet->getCell('C3')->getCalculatedValue());
+
+        $sheet->getCell('D1')->setValue('=CONCATENATE(A1,A1)');
+        self::assertSame('#VALUE!', $sheet->getCell('D1')->getCalculatedValue());
+        $sheet->getCell('D2')->setValue('=TEXTJOIN(",",TRUE,A2,A3)');
+        self::assertSame('#NUM!', $sheet->getCell('D2')->getCalculatedValue());
+        $sheet->getCell('D3')->setValue('=REPT(A3,3)');
+        self::assertSame('#DIV/0!', $sheet->getCell('D3')->getCalculatedValue());
+        $sheet->getCell('D4')->setValue('=CONCAT(A4,A4)');
+        self::assertSame('#NAME?', $sheet->getCell('D4')->getCalculatedValue());
+        $sheet->getCell('D5')->setValue('="X"&A4');
+        self::assertSame('#NAME?', $sheet->getCell('D5')->getCalculatedValue());
+        $sheet->getCell('D6')->setValue('=A2&"X"');
+        self::assertSame('#NUM!', $sheet->getCell('D6')->getCalculatedValue());
+
+        $sheet->getCell('E1')->setValue('=LEFT(A1)');
+        self::assertSame('#VALUE!', $sheet->getCell('E1')->getCalculatedValue());
+        $sheet->getCell('E2')->setValue('=RIGHT(A2)');
+        self::assertSame('#NUM!', $sheet->getCell('E2')->getCalculatedValue());
+        $sheet->getCell('E3')->setValue('=MID(A3,2,2)');
+        self::assertSame('#DIV/0!', $sheet->getCell('E3')->getCalculatedValue());
+        $sheet->getCell('E4')->setValue('=TEXTBEFORE(A4,"M")');
+        self::assertSame('#NAME?', $sheet->getCell('E4')->getCalculatedValue());
+        $sheet->getCell('E5')->setValue('=TEXTAFTER(A5,"U")');
+        self::assertSame('#VALUE!', $sheet->getCell('E5')->getCalculatedValue());
+
+        $sheet->getCell('F1')->setValue('=VALUETOTEXT(A1)');
+        self::assertSame('#VALUE!', $sheet->getCell('F1')->getCalculatedValue());
+        $sheet->getCell('F2')->setValue('=DOLLAR(A2)');
+        self::assertSame('#NUM!', $sheet->getCell('F2')->getCalculatedValue());
+        $sheet->getCell('F3')->setValue('=FIXED(A3)');
+        self::assertSame('#DIV/0!', $sheet->getCell('E3')->getCalculatedValue());
+        $sheet->getCell('F4')->setValue('=TEXT(A4,"M")');
+        self::assertSame('#NAME?', $sheet->getCell('F4')->getCalculatedValue());
+        $sheet->getCell('F5')->setValue('=VALUE(A2)');
+        self::assertSame('#NUM!', $sheet->getCell('F5')->getCalculatedValue());
+        $sheet->getCell('F6')->setValue('=NUMBERVALUE(A3)');
+        self::assertSame('#DIV/0!', $sheet->getCell('F6')->getCalculatedValue());
+
+        $sheet->getCell('G1')->setValue('=REPLACE("oldtext",2,2,A1)');
+        self::assertSame('#VALUE!', $sheet->getCell('G1')->getCalculatedValue());
+        $sheet->getCell('G2')->setValue('=SUBSTITUTE(A2,"U","V")');
+        self::assertSame('#NUM!', $sheet->getCell('G2')->getCalculatedValue());
+
+        $sheet->getCell('H1')->setValue('=FIND(A1, "U")');
+        self::assertSame('#VALUE!', $sheet->getCell('H1')->getCalculatedValue());
+        $sheet->getCell('H2')->setValue('=SEARCH(A2,"U")');
+        self::assertSame('#NUM!', $sheet->getCell('H2')->getCalculatedValue());
+
+        $sheet->getCell('I1')->setValue('=LEN(A1)');
+        self::assertSame('#VALUE!', $sheet->getCell('I1')->getCalculatedValue());
+        $sheet->getCell('I2')->setValue('=EXACT(A2,A2)');
+        self::assertSame('#NUM!', $sheet->getCell('I2')->getCalculatedValue());
+        $sheet->getCell('I3')->setValue('=T(A3)');
+        self::assertSame('#DIV/0!', $sheet->getCell('I3')->getCalculatedValue());
+        $sheet->getCell('I4')->setValue('=TEXTSPLIT(A4,"M")');
+        self::assertSame('#NAME?', $sheet->getCell('I4')->getCalculatedValue());
+
+        $sheet->getCell('J1')->setValue('=TRIM(A1)');
+        self::assertSame('#VALUE!', $sheet->getCell('J1')->getCalculatedValue());
+        $sheet->getCell('J2')->setValue('=CLEAN(A2)');
+        self::assertSame('#NUM!', $sheet->getCell('J2')->getCalculatedValue());
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php b/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
index d3f0ad664..d8de97a33 100644
--- a/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
@@ -6,6 +6,7 @@ namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\AdvancedValueBinder;
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
+use PhpOffice\PhpSpreadsheet\Cell\DataType;
 use PhpOffice\PhpSpreadsheet\Cell\IValueBinder;
 use PhpOffice\PhpSpreadsheet\Settings;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
@@ -232,4 +233,31 @@ class AdvancedValueBinderTest extends TestCase
             ["Hello\nWorld", true],
         ];
     }
+
+    /**
+     * @dataProvider formulaProvider
+     */
+    public function testFormula(string $value, string $dataType): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+
+        $sheet->getCell('A1')->setValue($value);
+        self::assertSame($dataType, $sheet->getCell('A1')->getDataType());
+        if ($dataType === DataType::TYPE_FORMULA) {
+            self::assertFalse($sheet->getStyle('A1')->getQuotePrefix());
+        } else {
+            self::assertTrue($sheet->getStyle('A1')->getQuotePrefix());
+        }
+
+        $spreadsheet->disconnectWorksheets();
+    }
+
+    public static function formulaProvider(): array
+    {
+        return [
+            'normal formula' => ['=SUM(A1:C3)', DataType::TYPE_FORMULA],
+            'issue 1310' => ['======', DataType::TYPE_STRING],
+        ];
+    }
 }
diff --git a/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php b/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php
index 43ac2fbd1..71006fff8 100644
--- a/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php
@@ -211,13 +211,19 @@ class StringValueBinderTest extends TestCase
         $cell->setValue($value);
         self::assertSame($expectedValue, $cell->getValue());
         self::assertSame($expectedDataType, $cell->getDataType());
+        if ($expectedDataType === DataType::TYPE_FORMULA) {
+            self::assertFalse($sheet->getStyle('A1')->getQuotePrefix());
+        } else {
+            self::assertTrue($sheet->getStyle('A1')->getQuotePrefix());
+        }
         $spreadsheet->disconnectWorksheets();
     }
 
     public static function providerDataValuesSuppressFormulaConversion(): array
     {
         return [
-            ['=SUM(A1:C3)', '=SUM(A1:C3)', DataType::TYPE_FORMULA, false],
+            'normal formula' => ['=SUM(A1:C3)', '=SUM(A1:C3)', DataType::TYPE_FORMULA],
+            'issue 1310' => ['======', '======', DataType::TYPE_STRING],
         ];
     }
 
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/MultiLineCommentTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/MultiLineCommentTest.php
new file mode 100644
index 000000000..f6fd5657a
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/MultiLineCommentTest.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
+
+use PhpOffice\PhpSpreadsheet\Reader\Ods;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class MultiLineCommentTest extends AbstractFunctional
+{
+    public function testMultipleParagraphs(): void
+    {
+        $filename = 'tests/data/Reader/Ods/issue.4081.ods';
+        $reader = new Ods();
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        self::assertSame("First line.\n\nSecond line.", $sheet->getComment('A1')->getText()->getPlainText());
+        $spreadsheet->disconnectWorksheets();
+    }
+
+    public function testOneParagraphMultipleSpans(): void
+    {
+        $spreadsheetOld = new Spreadsheet();
+        $sheetOld = $spreadsheetOld->getActiveSheet();
+        $sheetOld->getCell('A1')->setValue('Hello');
+        $text = $sheetOld->getComment('A1')->getText();
+        $text->createText('First');
+        $text->createText(' line.');
+        $text->createText("\n");
+        $text->createText("\n");
+        $text->createText("Second line.\nThird line.");
+        $spreadsheet = $this->writeAndReload($spreadsheetOld, 'Ods');
+        $spreadsheetOld->disconnectWorksheets();
+
+        $sheet = $spreadsheet->getActiveSheet();
+        self::assertSame("First line.\n\nSecond line.\nThird line.", $sheet->getComment('A1')->getText()->getPlainText());
+        $spreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2581Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2581Test.php
new file mode 100644
index 000000000..6ba87bd53
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2581Test.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
+use PHPUnit\Framework\TestCase;
+
+class Issue2581Test extends TestCase
+{
+    private static string $testbook = 'tests/data/Reader/XLSX/issue.2581.xlsx';
+
+    public function testIssue2581(): void
+    {
+        // CELL function (unimplemented) embedded in another function
+        $filename = self::$testbook;
+        $reader = new Xlsx();
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        self::assertSame('=CONCATENATE("Prefix ",MID(CELL("filename"),FIND("]",CELL("filename"))+1,255), " Suffix")', $sheet->getCell('B1')->getValue());
+        self::assertSame('Prefix SomeName Suffix', $sheet->getCell('B1')->getCalculatedValue());
+        $spreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/data/Cell/DefaultValueBinder.php b/tests/data/Cell/DefaultValueBinder.php
index b9f3d51e1..bd4295c0b 100644
--- a/tests/data/Cell/DefaultValueBinder.php
+++ b/tests/data/Cell/DefaultValueBinder.php
@@ -83,4 +83,7 @@ return [
         's',
         '1234567890123459012345689012345690',
     ],
+    'Issue 1310 Multiple = at start' => ['s', '======'],
+    'Issue 1310 Variant 1' => ['s', '= ====='],
+    'Issue 1310 Variant 2' => ['s', '=2*3='],
 ];
diff --git a/tests/data/Reader/Ods/issue.4081.ods b/tests/data/Reader/Ods/issue.4081.ods
new file mode 100644
index 000000000..6d690bd4e
Binary files /dev/null and b/tests/data/Reader/Ods/issue.4081.ods differ
diff --git a/tests/data/Reader/XLSX/issue.2581.xlsx b/tests/data/Reader/XLSX/issue.2581.xlsx
new file mode 100644
index 000000000..82af1c627
Binary files /dev/null and b/tests/data/Reader/XLSX/issue.2581.xlsx differ