Everything despawning constantly

I've had this problem where literally everything despawns, sometimes seconds after spawning. Recently I noticed that all of my villagers were disappearing. So I relocated them to my house, and I lit everything up and spawned an iron golem. Still vanishing. I named my villagers, blocked off any exits, and even played on peaceful mode, and they still despawn. My farm animals have this issue too. The despawn rates are insane.