Microsoft Word files going invisible in Word for Mac

In the last few days, I've been having an issue where certain Microsoft Word files have become invisible on a Mac. It doesn't happen to every Word document that is being actively worked on, but it does only affect Word files (not Excel, Powerpoint files etc.). I've tried to replace the 'invisible' files by pasting a new copy in, but I just get an error message that "The item "X" can't be replaced because it's invisible". If I hit command-shift-full stop, the invisible file shows up in the finder. It's greyed out but it can be opened but can't be selected to attached, say, to e-mails. This is severely impacting my ability to send files to people!

This is happening when I am working Mac-to-Mac (so working on one mac but pulling the files from the server of another mac), but the files are also invisible on the original mac that the files were pulled from.

Any help would be very, very gratefully received!