If you put the text string of the message you are receiving (“This document’s file has been changed by another application since you opened or saved it. The changes made by the other application will be lost if you save. Save anyway?”) into Google, you’ll see that hundreds (thousands) of cases are returned where applications of many kinds can behave that way.
IOW I don’t think it’s a message specifically from RW.
If I’m right, then it suggests it’s something else happening other than from within RW. Not sure what - and I appreciate that this appears to have started with RW 7. That must be very disconcerting for you
May I suggest you try looking at the threads which are returned from this (Google) search: could it be that the file is locked, has been copied and renamed in an order that the OS can’t follow; (previously) in DropBox etc. I suspect it’s some sort of date and time issue that is confusing the OS, not RW.
Fixing it, of course, is another challenge. But to know that the message is masking another circumstance may be a good way to start. Good luck!