Villagers despawning

So I tried reviving a village started by curing two zombie villagers and they started breeding and it seemed as the it was going to be a successful village but then villagers started disappearing and I know for a fact it wasn’t any mobs killing them because I had walled off the village and put many torches and made sure there weren’t any mobs spawning tried many times to revive village but kept getting same result even put 2 iron golems just in case mobs were spawning with out me noticing but even the iron golems despawned