Problems with Apple Photos I recently spent hours organizing my folders and files with Mac Photo on one of my Macs. Now, a few days later, all my changes are gone and everything is back to the way it was before the big cleanup, and the way it is on my other Mac. Any idea why this happened and how I can prevent it from happening again?
I can't guess what corrupted the files or the database, but Time Machine would allow you to roll back whatever corruption or changes you don't like and get back to a point in time.

To do that, open Time Machine and restore the library file / overwriting the wrong version.