[12:02:42] [File IO Thread/ERROR] [net.minecraft.world.chunk.storage.AnvilChunkLoader]: Failed to save chunk
java.util.ConcurrentModificationException: null
	at java.util.HashMap$HashIterator.nextNode(Unknown Source) ~[?:1.8.0_241]
	at java.util.HashMap$KeyIterator.next(Unknown Source) ~[?:1.8.0_241]
	at net.minecraft.nbt.NBTTagCompound.func_74734_a(NBTTagCompound.java:27) ~[fy.class:?]
	at net.minecraft.nbt.CompressedStreamTools.func_150663_a(CompressedStreamTools.java:112) ~[gi.class:?]
	at net.minecraft.nbt.CompressedStreamTools.func_74800_a(CompressedStreamTools.java:102) ~[gi.class:?]
	at net.minecraft.world.chunk.storage.RegionFileCache.getChunkOutputStream(RegionFileCache.java:139) ~[ayk.class:?]
	at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_183013_b(AnvilChunkLoader.java:244) ~[aye.class:?]
	at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75814_c(AnvilChunkLoader.java:220) [aye.class:?]
	at net.minecraft.world.storage.ThreadedFileIOBase.func_75736_b(SourceFile:37) [bgx.class:?]
	at net.minecraft.world.storage.ThreadedFileIOBase.run(SourceFile:30) [bgx.class:?]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_241]