I assume you have saved or closed it since the “event” – (and so undoing until it is fixed, isn’t an option).
Support may have a way to fix it, but I would make a copy of your working document and convert to unformated citations and clean up any other field codes after that. (on a PC, I do that with select all, then ctrl+shift+F9)
Option 1. You can then reinsert the citations that moved.
OR
Option 2. you can go back to an earlier back up version before the corruption, and make a copy of that and also unformat the citations.
Using words tools in “review” tab, Compare the two, and keep your new changes, but reject the shifted citations, keeping the originals. Then you should have a clean document reflecting your current version and the corrected citations.