Villagers, Chickens etc tend to become non entities. Logging in and out doesn't bring them back, restarting the server doesn't bring them back, they seem to just get deleted from the game. The only way I've found to fix this is to restore from backup.
I found that if I put these things in mine carts they don't go away from the game.
Note: they don't become invisible they are just gone from the game only a map restore from back will bring them back from what I can see.
Linked issues
is duplicated by 12
MC-85196
Animal/Villager disappear permanently upon loading an area
Resolved
MC-85282
Mobs dissapear
Resolved
MC-85298
Villager despawning issue
Resolved
MC-85322
Command block minecarts become invisible after dying in Survival/Adventure
Resolved
MC-85325
map in itemframe disappears
Resolved
relates to 2
Attachments
Comments 11
Please attach the server.log.
Most likely MC-82945
I don't think it's a dup of that issue because the entities never disappeared until I went to week 32 snapshots.. week 31 I had no problems.
From the logs:
[08:34:21] [Server thread/WARN]: Tried to add entity Sheep with duplicate UUID 630d64a8-1cc7-4338-ad00-ac0da584a3d6
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID a87cbb9c-c471-4d1d-a77f-8d1e808fd579
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID 2a33a86c-926c-43d0-8bc8-a58385caf1ba
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID c6bc86aa-ec75-4176-b481-7834858ab911
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID 9869c897-e0dc-4f4a-88ca-44fbf93ea81c
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID 08abb574-d97e-43d4-b584-948ce60e8fcd
[08:35:06] [Server thread/WARN]: Tried to add entity Item with duplicate UUID f05fc33c-ce9c-4784-8af7-3eccacc73679
[08:35:06] [Server thread/WARN]: Tried to add entity Item with duplicate UUID 9a776055-0597-42a5-bf23-eef79640aa45
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID e05bc3c4-9f8c-494e-ba46-1ca60fd94cd2
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID 834b9721-c979-44d5-8f6c-52542b9042f8
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID 197ef31b-e849-458c-aafa-716b5c145d6f
[08:35:06] [Server thread/WARN]: Tried to add entity Item with duplicate UUID afbc4a75-b67f-4027-a790-0578b92c4ff2
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID 42df4afa-dbf4-489e-8366-679e8c24fc38
[08:35:06] [Server thread/WARN]: Tried to add entity Chicken with duplicate UUID 5d8bbd0e-4aca-4cb0-ad9d-f0702df53c06
... some hundred lines omitted ...Upon further testing, it appears that when a player enters the End exit portal, all entities which are within view distance of spawn but not in the spawn chunks are deleted.
A player does not need to enter an end portal for this to occur. I was no where near a portal when I tested the snapshot. None of the entities where moving into portals. They all just vanished. My world was created before 1.7, but the vast majority of the entities around me where spawned during 1.8. None remained.
Happened to me as well