Issue with UndoRecord.StartCustomRecord in VSTO add-in: Undo stack breaks after bullet/numbering

I am using UndoRecord.StartCustomRecord in Microsoft.Office.Interop.Word to create custom undo records in my VSTO add-in. However, I’ve encountered some unexpected behavior that makes the Word undo stack unusable.

Here’s what I did:

• From a button click, I performed a Find and Replace operation and applied styles using the set_Style() method.
• These actions were wrapped inside UndoRecord.StartCustomRecord and UndoRecord.EndCustomRecord.

Issue: When I try to perform these custom actions after adding bullets or numbering, my custom undo record does not appear in the Undo stack as expected. Instead:

• The “Replace All” operation gets unfolded (treated as a separate undo steps rather than a single custom action).
• I can no longer undo actions that occurred before my custom action execution.

This essentially breaks the Undo stack.

Code snippet I used:

Word.Range currentRange = Globals.ThisAddIn.Application.Selection.Range;

var application = Globals.ThisAddIn.Application;
var document = application.ActiveDocument;

this.undoRecord = application.UndoRecord;

this.undoRecord.StartCustomRecord("MyRecord");
string replacementText = "";

Word.Find find = currentRange.Find;
find.ClearFormatting();
find.Replacement.ClearFormatting();
find.Text = "^p"; // Paragraph break
find.Replacement.Text = replacementText;
find.Forward = true;
find.Wrap = Word.WdFindWrap.wdFindStop;
find.Format = false;
find.MatchCase = false;
find.MatchWholeWord = false;
find.MatchWildcards = false;
find.Execute(Replace: Word.WdReplace.wdReplaceAll);

foreach (Word.Paragraph paragraph in document.Paragraphs)
{
    paragraph.Range.set_Style(Microsoft.Office.Interop.Word.WdBuiltinStyle.wdStyleEmphasis);
}

this.undoRecord.EndCustomRecord();

I made a sample project in GitHub to recreate this issue. You can build the GitHub sample and try to recreate the issue. Following are the recreation steps.

• Add some paragraphs to the document
• Add a number or bullet from Numbering menu.
• Click on the top button in my VSTO plugin.
• Custom undo action doesn't reflect properly in Undo stack
• If the same actions were done to a document without bullets or numbering, undo stack will be unharmed and will work properly.

Am I using UndoRecord.StartCustomRecord incorrectly, or is this a limitation/bug in Word’s undo stack? How should I correctly implement custom undo records in this scenario?