[18:14:47] [Server thread/ERROR]: Encountered an unexpected exception
java.util.ConcurrentModificationException: null
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429) ~[?:1.8.0_72]
	at java.util.HashMap$KeyIterator.next(HashMap.java:1453) ~[?:1.8.0_72]
	at net.minecraft.server.v1_12_R1.EntityTracker.updatePlayers(EntityTracker.java:180) ~[spigot-1.12.2.jar:git-Spigot-4bd94dc-f4ca180]
	at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:834) ~[spigot-1.12.2.jar:git-Spigot-4bd94dc-f4ca180]
	at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) ~[spigot-1.12.2.jar:git-Spigot-4bd94dc-f4ca180]
	at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) ~[spigot-1.12.2.jar:git-Spigot-4bd94dc-f4ca180]
	at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [spigot-1.12.2.jar:git-Spigot-4bd94dc-f4ca180]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_72]