Villagers despawning

Villager dissapear when I go a certain distance away such as 200 blocks. I will come back and there will only be 1 or 2 villagers left at random. This includes villagers I’ve traded with and baby villagers that I’ve bred. I’ve even tried naming villagers to stop them despairing when I leave. Very irritating as I cannot utilise villager trading at all as they keep despawning.