This error still occurs and is also referenced on this thread (although not the original subject of th thread):
Citation works in a new document or other old documents but in a particular document citations can no longer be added - it just hangs showing “formatting citation”. The reason seems to be the libreoffice file seems to get corrupted - if the document content is copied as unformatted text (i.e. without the citation fields) then it will work but that is not very helpful if you need to keep citations editable.
The problem does not seem to be due to a single corrupt field because copying alone any one citation field to a new document recreates the problem in the new document unless copied as unformatted text.
Any idea if it’s possible to recover the file properly?
I have had a similar problem occur before due to track changes and managed to recover the file by accepting all changes but not in this case.