Copying format restarts a custom undo record

Question

I'm developing a Word add-in using VSTO and faced an issue with a custom UndoRecord. The problem appears when I use the CopyFormat method between the StartCustomRecord and EndCustomRecord method calls. Executing CopyFormat causes the existing UndoRecord to close and start a new one. This results in an additional record appearing in the undo stack, which is not the desired behaviour.

Here is a simplified version of the method I'm using:

private static void PasteRtf(string rtf, Range sourceRange, Range targetRange)
{
    var undoRecord = sourceRange.Application.UndoRecord;
    try
    {
        undoRecord.StartCustomRecord("Custom record");

        targetRange.InsertParagraphBefore();
        targetRange = targetRange.Paragraphs.First.Range;

        System.Windows.Clipboard.Clear();
        System.Windows.Clipboard.SetData(System.Windows.DataFormats.Rtf, rtf);
        targetRange.Paste();

        sourceRange.Select();
        sourceRange.Application.Selection.CopyFormat();
        targetRange.Select();
        targetRange.Application.Selection.PasteFormat();
    }
    finally
    {
        undoRecord.EndCustomRecord();
    }
}

In the above code, StartCustomRecord is called at the beginning, and EndCustomRecord is called at the end. However, after executing CopyFormat, it seems that a new UndoRecord is created, which results in multiple undo actions for a single operation.

My questions are:

1. Why does CopyFormat cause a new UndoRecord to be created?
2. How can I prevent this behavior and ensure that only one undo record is created for the entire operation?

Any insights or suggestions would be greatly appreciated. Thanks in advance!