In my player-created village, villagers repeatedly despawn. It is surrounded by a wall that can't be climbed over, and it is flooded with light to prevent any mobs from spawning inside the wall. Multiple iron golems patrol inside as well. My point is that there is no in-game reason for me to be losing villagers. However, nearly a dozen villagers have disappeared since the village was populated. They would be born and become adults, but if i ever saved and quit or ventured far enough for the village to disappear, then a few would be missing when i returned. Which ones disappear seems to be random. I have tried to keep them breeding as much as possible to prevent my village from completely dying out, but losing multiple master level traders is frustrating. The switch version seems to be less optimized in general, so i would guess it has something to do with the game glitching when it tries to load the mobs in. Cows, pigs, and iron golems have persisted well while chickens, sheep, and mainly villagers have not.