Here's another trace related to DocumentPosition.

On  editor.Document.GetAllRevisions();

System.​InvalidOperationException: Failed to compare two elements in the array.​
---> System.​NullReferenceException: Object reference not set to an instance of an object.​
   at Telerik.​Windows.​Documents.​DocumentPosition.​.​ctor(RadDocument document) in D:\a\1\s\Controls\RichTextBox\Core\DocumentPosition\DocumentPosition.​cs:line 111
   at Telerik.​Windows.​Documents.​Model.​Revisions.​Revision.​CalculateSelectionRange() in D:\a\1\s\Controls\RichTextBox\Core\Model\Revisions\Revision.​cs:line 209
   at Telerik.​Windows.​Documents.​Model.​Revisions.​RevisionCollection.​RevisionComparison(Revision r1, Revision r2) in D:\a\1\s\Controls\RichTextBox\Core\Model\Revisions\RevisionCollection.​cs:line 293
   at System.​Collections.​Generic.​ArraySortHelper`1.​InsertionSort(Span`1 keys, Comparison`1 comparer)
   at System.​Collections.​Generic.​ArraySortHelper`1.​IntroSort(Span`1 keys, Int32 depthLimit, Comparison`1 comparer)
   at System.​Collections.​Generic.​ArraySortHelper`1.​Sort(Span`1 keys, Comparison`1 comparer)
   --- End of inner exception stack trace ---
   at System.​Collections.​Generic.​ArraySortHelper`1.​Sort(Span`1 keys, Comparison`1 comparer)
   at Telerik.​Windows.​Documents.​Model.​Revisions.​RevisionCollection.​Recalculate() in D:\a\1\s\Controls\RichTextBox\Core\Model\Revisions\RevisionCollection.​cs:line 62
   at WorkingPaperSystem.​Controls.​RichText.​ConvertRadToDocx(RichTextEditWindow richTextEditWindow) in E:\Projects2\Composer Suite\Working Paper System\Composer-WPF\Controls\RichText.​xaml.​cs:line 796

I was expecting that you could tell me what could be NULL at line 1063 of DocumentPresenterBase.​cs, to orient my tests? I still don't know how to reproduce. In one case, the user told me that he was trying to adjust column width in a table and row height.

By the way: version 2026.1.415

With the .pdb, I've got the lines of the errors (still don't know how to reproduce, if you have an idea based on the trace ??):

 

System.​NullReferenceException: Object reference not set to an instance of an object.​

   at Telerik.​Windows.​Documents.​UI.​DocumentPresenterBase.​CaretPosition_​PositionChanged(Object sender, EventArgs e) in D:\a\1\s\Controls\RichTextBox\Core\UI\DocumentPresenterBase.​cs:line 1063

   at Telerik.​Windows.​Documents.​DocumentPosition.​MoveToPosition(DocumentPosition newPosition) in D:\a\1\s\Controls\RichTextBox\Core\DocumentPosition\DocumentPosition.​cs:line 1856

   at Telerik.​Windows.​Documents.​Selection.​MouseSelectionHandler.​UpdateSelectionAndCaretPosition() in D:\a\1\s\Controls\RichTextBox\Core\Selection\MouseSelectionHandler.​cs:line 691

   at Telerik.​Windows.​Documents.​Selection.​MouseSelectionHandler.​RegisterDocumentMouseMove(Point position, SourceType source) in D:\a\1\s\Controls\RichTextBox\Core\Selection\MouseSelectionHandler.​cs:line 417

   at Telerik.​Windows.​Documents.​UI.​DocumentPresenterBase.​HandleMouseMoveOnPosition(Point position, SourceType source) in D:\a\1\s\Controls\RichTextBox\Core\UI\DocumentPresenterBase.​cs:line 734

   at Telerik.​Windows.​Documents.​UI.​DocumentPresenterBase.​Owner_​MouseMove(Object sender, MouseEventArgs e) in D:\a\1\s\Controls\RichTextBox\Core\UI\DocumentPresenterBase.​cs:line 729

   at System.​Windows.​EventRoute.​InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)

   at System.​Windows.​UIElement.​RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)

   at System.​Windows.​Input.​InputManager.​ProcessStagingArea()

   at System.​Windows.​Interop.​HwndMouseInputProvider.​ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)

   at System.​Windows.​Interop.​HwndMouseInputProvider.​FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)

   at System.​Windows.​Interop.​HwndSource.​InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)

   at MS.​Win32.​HwndWrapper.​WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)

   at System.​Windows.​Threading.​ExceptionWrapper.​InternalRealCall(Delegate callback, Object args, Int32 numArgs)

   at System.​Windows.​Threading.​ExceptionWrapper.​TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

I'm using Binaries.NoXaml\WPF80. Do you mean Telerik.Windows.Documents.Core.pdb and Telerik.Windows.Controls.RichTextBox.pdb?

Thanks for the info.

Any breaking changes in 2026? The problem started after first 2026 update.

I don't want to publish all the .PDB since it will make the application too big. Any minimal ones to include to get the exception line in Telerik.Windows.Documents.UI.DocumentPresenterBase.CaretPosition_PositionChanged?

We have users everywhere in the world in different time zone so I'm not able to get in touch with them right away in order to know how to reproduce the problem. I was hoping that you could give me so guidance on what I could try to reproduce the problem based on the CaretPosition_PositionChanged code where object can be null and also on what has changed in the richtexteditor since last version. On our side, nothing changed on the way we use the editor. 

Is it possible to get a .pdb file that we can deploy with your DLLs to at least get the line of the "object reference no set to an instance of an object"?

Meanwhile, I'll try to reproduce in debug, but it will help to know what to try that could affect the caret position.