Cloned villager pops up out of nowhere

Alright, so this is weird and I don't know how to replicate this. In my village I got one villager. Cured from a zombie. There is also an iron golem nearby. Then in the latest snapshot I was returning to my village to see a second villager popping up. It was the exact same one, a farmer with the same trades, all unlocked. It didn't dissapear, there isn't a generated village in my world. It popped out of nowhere.

I did mess with some world backups of mine, switching around between them, but I don't know if that could've caused this behaviour. It never did before and I was messing with backups a lot before this event.

What happened?