Description:

When running AbyssalCraft, logs spammed with duplicate UUID conflicts for abyssalcraft:abyssalzombie
(even when nobody is on the server, therefore the assumption of chunkloading by not saving on unload)

Crash report:

Affected versions ("latest" is NOT a version):

• Minecraft: minecraft_server.1.12.2.jar
• Forge: forge-1.12.2-14.23.4.2757-universal.jar
• AbyssalCraft: AbyssalCraft-1.12.2-1.9.4.11.jar

Latest log file for when the issue was present:

https://gist.github.com/CatRabbit499/d86f91eab13bdcbf214650e6f6d85c8a

That's likely due to them killing regular zombies, then picking up their drops (mostly rotten flesh), which in turn prevents them from despawning. There's a section in the config file for item blacklists used to prevent mobs capable of picking up stuff from picking up specific items. I plan on setting this as the default values in the config file:

minecraft:rotten_flesh
minecraft:bone
abyssalcraft:antiflesh
abyssalcraft:corflesh
abyssalcraft:anticorflesh