Villagers missing, villagers despawning, villagers vanishing

I am playing on a server I created for myself and only I play on it (PC java edition). I had a village, next to which I live, with around 15 villagers. But when I came from mining there were only around 5 villagers left and 7 iron golems, that spawned naturally. I have my village secured with wall that cant be jumped over and everything is lit up, so I dont think mobs killed them. Also I dont think it was raid, because no raid bar was shown and no walls destroyed, only if pillagers can open fence gates, then they could get in.

What do you think? What caused it? Why did they vanish?

Thank you for resolving.