4 hour gap in CC backups

My computer shutdown unexpectedly while I was working on a session. When it booted back up, I went to recover my project (I have it set to backup every 3 minutes to creative cloud). I noticed that the most recent backup was from 4 hours prior. (this screenshot of the creative cloud app was taken 11 minutes after restart, so the two at the top are post-shutdown).

I had the session open continuously during that 4-hour period, during which I saved it many times manually. Yet upon restart, it had reverted to the 4-hour old version and the most recent creative cloud backup was also 4 hours old. I was fortunately able to recover the session from an icloud backup, but I would like to know why this happened so as to avoid it happening again in the future.