This is a big problem. When you close a document after making changes it automatically saves the file. It really needs to say “do you want to saves changes”. Sometimes you make some changes that you regret.
It may be a System Preference problem.
And so it was. Thank you so much!
Also do note that you can always choose ‘File > Revert To > Browse All Versions…’ since the new system keeps a lot of data around!