I keep getting error 4 damaged document, cannot save, in Indesign 13.1

It stops me from saving or opening files. I have to quit Indesign 13.1 before I can proceed. Then it seems to work. I have deleted the cache as suggested countless times, it still happens. I have a feeling it's something to do with Illustrator 22.1, when I open that to work on a file and then quit it. It is then that I seem to get the error code 4 in indesign. Can you please advise.