Not sure about the F_chbook, etc., but I'm wondering if you might have created a duplicate source, or if in updating your data the source may have become duplicated. Try looking through your existing source records to see if you can find the culprit. From the Build menu, choose Source Record. Locate the source from the find button by typing any part of abbrev 1 or 2. Click on show to see a list of those found.
If you locate it and want to delete the source, select it from the Evidence List. Click selected to remove it ... making SURE you don't select ALL (that removes all sources from the list). If you are using the Advanced Editing mode, you may have to manually edit or remove footnotes if you created any. The Normal Editing footnotes are automatically rebuilt.
Not sure if this will answer all of your question, but hope it at least helps a bit.