I have found that villagers unlike the other passive mobs will jump off cliffs to get the shortest path to a bed or a work station. They seem to jump when it is 4 to 5 blocks high, which ends up killing them! Please fix this as it has caused me to have to constantly cure zombie villagers to try to rebuild the village. I would go off mining and come back with no villagers. Can Mojang please fix that part of their AI to be like passive mobs. It would be part of the "vanishing" villager problem.