Description:
Undoing a deletion of text with fieldmarks moves the closing fieldmark 2 chars right. Further redo/undo actions cause more destruction.

Steps to Reproduce:
1. Here (see attachment) is a simple document containing a fieldmark pair (generated using the script from bug 116960). The fieldmarks are between || vertical line characters. Select everything between | characters (inclusively, to be sure you also select both invisible fieldmark characters).
2. Press Del.
3. Press Undo.

Actual Results:
The closing fieldmark (and the shading) has moved 2 characters right, including the gray shading. [To have more fun: Press Redo. More text is deleted than the first time. Press Undo again. Different things can happen depending on your version. An assertion crash, removal of the first fieldmark etc.]

Expected Results:
Proper undo of fieldmark deletion.


Reproducible: Always


User Profile Reset: No



Additional Info:
The earliest version where the bug can be reproduced exactly is 4.2.1.1. In 4.2.0.4, I can't select anything, 4.2.0.3 Mac download is missing, 4.1.6.2 and 4.2.0.2 do not let you delete fieldmarks, 3.6.7.2 seems to work properly.