Advice on working with a backup file

I recently opened a zip backup file to work with as a test. I added some text and saved it. But when I came to open it again, a message saying another file was open on another computer/or the file I was trying to open had not been closed properly, so the current file would have to be synchronised. (This is how I remember it, so I might not be entirely correct in my description of event and the sequence). But I couldn’t see another file open and I am only using the one Mac. Eventually, after a new icon appeared, a message said this file was an older version and would have to be undated. I’ve no idea why this happened, as I am using the most recent version of Scrivener. I clicked to update but there was no text in the update. However, I found a copy in Documents with only a small amount of the recent work I did missing.

I want to avoid this kind of trouble again if I need to work from a backup. Please advise on the best way to work with a backup zip file. And regards backup housekeeping, what do you advise when making zip backups? Each backup is given a new name (date). I suppose it is best to delete earlier versions. Is that sensible?

I use OS X’s built-in compression for zipping files that I’ve already saved and closed. I’ve got the idea that I’m less likely to end up with a corrupt file if I start with work that’s already closed. Besides, it’s how I started doing my backups when I began, and I’m reluctant to stop now that I’m in the good habit.

As far as the housekeeping end of it goes, I’m a bit obsessive. I keep absolutely everything.