Undo people renaming that has gone very wrong?

I have some 34.000 photos in my library, and close to 17.000 faces on those photos were named through Lightroom Classic. Today I went to correct a few face names in a few individual photos and during that action Lightroom Classic froze. When Lightroom started working again, every recognized face in my whole library have been identified as a one and only person, all other (over 200 individuals) are gone. I have no idea what happened, I am quite sure I did not somehow select all photos and remove/change all persons to this one. If I need to revert back to an old backup library, tens of hours of developing and metadata work will be ruined. I guess that there is no such way - but if someone does happen to have an idea of a way to get back the database fields holding the person identification data from old backups without reverting other things to the backup version that would be a great help!

Thanks, 

Benjamin

Lightroom Classic 12.1 / Windows 11 / People face recognition -> renaming