Occasionally after curing Zombie Villagers and closing the server, upon starting up the server again Villagers will despawn. Circumstances unknown: doesn't happen 100% of the time. Server world autosaving was turned on. Despawned Villagers were a Shepherd and a Leatherworker. The Cleric cured around the same time still remained. This is not an issue with the server using an older version of minecraft that doesn't have the new Villager professions, for previously cured Fishermen and Toolsmiths remained in the world.

Steps to reproduce:
1. Start up a server.
2. Cure a Zombie Villager.
3. Once the Villager is cured,close the server.
4. Upon reloading the server, the cured Villager will sometimes disappear.