Just lost most of my People identifications

Since the last system update, Photos seems to have lost most of its People identifications.

I noticed it randomly at first, but after checking more closely, it looks like a large portion of the photos that were previously assigned to people are no longer identified.

I'm currently running Photos Version 26.5 (25F71).

One thing that made me realise something was wrong is that I have a Smart Album that automatically collects photos containing unnamed faces. Before the update it was almost empty, but today it suddenly contains nearly 900 photos.

It's been like this for about three days now, so I doubt it's simply a matter of the library continuing to scan and update itself in the background.

Has anyone else experienced this? Do you know what could have caused it, and more importantly, is there a way to rebuild or repair the People database without starting from scratch, which would be pretty f***ing annoying?