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Minecraft 1.12.2 Modded ConcurrentModificationException Crash


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Maybe this doesn't belong in the Forge Support Forums, but I have searched through many other sources with little luck.




Here is a copy of my debug file:
<script src="https://gist.github.com/Muddledde/e86f5b391256c346de3b28d067c6b884.js"></script>


The game crashes and gives:


Description: Exception in server tick loop

    at java.util.HashMap$HashIterator.nextNode(Unknown Source)
    at java.util.HashMap$ValueIterator.next(Unknown Source)
    at net.minecraft.world.World.func_147448_a(World.java:1949)
    at net.minecraft.world.chunk.Chunk.func_76631_c(Chunk.java:856)
    at net.minecraftforge.common.chunkio.ChunkIOProvider.syncCallback(ChunkIOProvider.java:109)
    at net.minecraftforge.common.chunkio.ChunkIOExecutor.tick(ChunkIOExecutor.java:150)
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:728)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668)
    at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:185)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
    at java.lang.Thread.run(Unknown Source)


More Detail


I have been putting together a Modpack (for myself, possibly with the idea of it being shared with others), and for some time now I have been crashing and receiving that error.


This crash happens:

  • When I return to a location that I previously visited (but not all the time)
  • When loading the game back up after the crash
    • When Minecraft is loading in the background, the Esc/Pause Menu will pop up and prevent the world from fully loading
      • Staying in this state will show what has visibly loaded behind the Esc screen
      • When selecting "Back to Game," there will be a tiny bit of loading/updating, and then the world will crash
    • Sometimes the game crashes before the loading can reach the Esc/Pause Menu
  • Rarely, in extreme circumstances, the crash will happen during the Minecraft Forge loading process (before the Minecraft Menu is reached)
  • Rarely, while loading the world, Minecraft will freeze and stop responding (I've let it run for an hour with no update)
    • I will have to End Task, which sometimes it gives that error, sometimes it apologizes for the crash, and sometimes it doesn't recognize that it crashed
    • Again, this is very rare


After the world loads into the Esc/Pause Menu, I can return to the game, long enough to see some things update, or even move a small bit, before the game crashes.

When I can move some, sometimes I can move ever so slightly back during each loading attempt, until I can move backwards away from the area that is causing me to crash.

Am I actually moving away from the issue? I don't know, but I've had the best luck with it.


The crash doesn't appear to happen when exploring. So far I've been able to just go in whatever direction for as long as I like, checking out new places.

It appears to happen only when I return to a place I haven't been to for a bit.

Also, it appears to happen only in places that I haven't placed anything in; but I haven't thoroughly tested that yet (I guess I could go around placing a torch in every chunk and see how that works :-D )


Things I've Tried


  • I checked to make sure that I have the latest versions of Java and Forge, and checked many of the other mods that I have added as well
  • I have looked into many of the mod's forums searching for this issue, and also posting in their forums (with little success)
  • I have slowly removed mods in attempt to see if there is a specific mod that is causing the issue
    • Though there hasn't been a definitive result from a mod removal, it feels as if removing Tinker's Construct does the trick, but only after the world is loaded a few more times after the mod is removed
      • Could just be coincidence
  • For some time, "Open to LAN" appears to have resolved the issue for a bit, but I think it was coincidence as well



I'm not sure what else to add here, but please inquire about anything that comes to mind! Thank you for taking the time to read over this, and I hope this can be resolved!

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