Updating to Photos 3.0 removed my Face tags

I have 4,800 pix in my photo library. I updated to Photos 3.0 a few weeks ago. Today I launched Photos for the first time since the update. I was shocked and angered when I saw that many, many, MANY of my previously-named Faces (now People in 3.0) have had the name tag changed to "Unnamed". I also have many pictures with people in them who were not tagged - i.e., old family photos with people I didn't know, so I left them blank. The previously-unnamed people are still unnamed, and no tag was added for them - good. But the other people in the pic who I DID name now show as 'Unnamed'.

I spent 2 hours on the phone with Apple Photos expert (and another 45 minutes on hold) who ran some obscure command in the terminal mode, did a 'repair' of the library, then finally told me to restore my library backup from Time Machine. Immediately after the restore, all the names were back again. But overnight, Photos again re-scanned all the pix in the restored library, and once again wiped out many of my tags.

I am so angry about this. I am sick to think of all the time I spent doing this work in the first place, and now it seems I'm going to have to do a good portion of it again. And what's to prevent it from happening again the next time there's an update to the Photos app?

What other photo organizing software should I consider using? What the eff is wrong with the Apple engineers who would release an update that would actively harm a user's data?