Time: 3/16/16 5:50 PM
Description: Exception ticking world

java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
    at java.util.HashMap$KeyIterator.next(HashMap.java:1453)
    at net.minecraft.server.v1_9_R1.PlayerChunkMap.flush(PlayerChunkMap.java:119)
    at net.minecraft.server.v1_9_R1.WorldServer.doTick(WorldServer.java:253)
    at net.minecraft.server.v1_9_R1.MinecraftServer.D(MinecraftServer.java:831)
    at net.minecraft.server.v1_9_R1.DedicatedServer.D(DedicatedServer.java:404)
    at net.minecraft.server.v1_9_R1.MinecraftServer.C(MinecraftServer.java:714)
    at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:613)
    at java.lang.Thread.run(Thread.java:745)


A detailed walkthrough of the error, its code path and all known details is as follows:
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-- Head --
Stacktrace:
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
    at java.util.HashMap$KeyIterator.next(HashMap.java:1453)
    at net.minecraft.server.v1_9_R1.PlayerChunkMap.flush(PlayerChunkMap.java:119)
    at net.minecraft.server.v1_9_R1.WorldServer.doTick(WorldServer.java:253)