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Multiplayer Server (Essential Mod) Crashes randomly and often in The End (exception in server tick loopError)

Posted July 23Jul 23

exception in server tick loopError: java.util.ConcurrentModificationException: null

Me and my friend had finally reached the end in our modpack, we summoned the dragon, took out the crystals seemingly smoothly but after we started to kill the dragon I (the host) started to have my game randomly crash, sometimes after a few seconds, sometimes after a minute and i can't really think of any conflicts that would be causing it, so i was wondering if anyone had any ideas on what could be the issue? I appriciate any help

Here's the crashlog,

https://mclo.gs/PZgd77N

---- Minecraft Crash Report ----
// Embeddium instance tainted by mods: [fusion, oculus]
// Please do not reach out for Embeddium support without removing these mods first.
// -------
// Hey, that tickles! Hehehe!

Time: 2025-07-23 23:34:35
Description: Exception in server tick loop

java.util.ConcurrentModificationException: null
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1597) ~[?:?] {}
at java.util.HashMap$KeyIterator.next(HashMap.java:1620) ~[?:?] {}
at java.lang.Iterable.forEach(Iterable.java:74) ~[?:?] {re:mixin}
at net.minecraft.server.level.DistanceManager.m_140805_(DistanceManager.java:119) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:classloading}
at net.minecraft.server.level.ServerChunkCache.m_8489_(ServerChunkCache.java:273) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:mixin,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:cupboard.mixins.json:ChunkLoadDebug,pl:mixin:A}
at net.minecraft.server.level.ServerChunkCache$MainThreadExecutor.m_7245_(ServerChunkCache.java:545) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:classloading}
at net.minecraft.server.level.ServerChunkCache.m_8466_(ServerChunkCache.java:269) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:mixin,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:cupboard.mixins.json:ChunkLoadDebug,pl:mixin:A}
at net.minecraft.server.MinecraftServer.m_129961_(MinecraftServer.java:758) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:mixin,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,re:classloading,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,pl:mixin:APP:structureessentials.mixins.json:LevelCreatedCallback,pl:mixin:APP:citadel.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:majruszlibrary-common.mixins.json:MixinMinecraftServer,pl:mixin:APP:mixins.essential.json:feature.sps.Mixin_IntegratedServerResourcePack,pl:mixin:APP:mixins.essential.json:server.MinecraftServerAccessor,pl:mixin:APP:mixins.essential.json:server.MinecraftServerMixin_PvPGameRule,pl:mixin:APP:mixins.essential.json:server.Mixin_ServerCoroutineScope,pl:mixin:APP:mixins.essential.json:server.Mixin_PublishServerStatusResponse,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetDifficulty,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetGameType,pl:mixin:A}
at net.minecraft.server.MinecraftServer.m_7245_(MinecraftServer.java:747) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:mixin,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,re:classloading,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,pl:mixin:APP:structureessentials.mixins.json:LevelCreatedCallback,pl:mixin:APP:citadel.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:majruszlibrary-common.mixins.json:MixinMinecraftServer,pl:mixin:APP:mixins.essential.json:feature.sps.Mixin_IntegratedServerResourcePack,pl:mixin:APP:mixins.essential.json:server.MinecraftServerAccessor,pl:mixin:APP:mixins.essential.json:server.MinecraftServerMixin_PvPGameRule,pl:mixin:APP:mixins.essential.json:server.Mixin_ServerCoroutineScope,pl:mixin:APP:mixins.essential.json:server.Mixin_PublishServerStatusResponse,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetDifficulty,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetGameType,pl:mixin:A}
at net.minecraft.util.thread.BlockableEventLoop.m_18701_(BlockableEventLoop.java:139) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:computing_frames,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:mixins.essential.json:client.Mixin_ThreadTaskExecutor,pl:mixin:A}
at net.minecraft.server.MinecraftServer.m_130012_(MinecraftServer.java:733) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:mixin,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,re:classloading,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,pl:mixin:APP:structureessentials.mixins.json:LevelCreatedCallback,pl:mixin:APP:citadel.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:majruszlibrary-common.mixins.json:MixinMinecraftServer,pl:mixin:APP:mixins.essential.json:feature.sps.Mixin_IntegratedServerResourcePack,pl:mixin:APP:mixins.essential.json:server.MinecraftServerAccessor,pl:mixin:APP:mixins.essential.json:server.MinecraftServerMixin_PvPGameRule,pl:mixin:APP:mixins.essential.json:server.Mixin_ServerCoroutineScope,pl:mixin:APP:mixins.essential.json:server.Mixin_PublishServerStatusResponse,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetDifficulty,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetGameType,pl:mixin:A}
at net.minecraft.server.MinecraftServer.m_130011_(MinecraftServer.java:665) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:mixin,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,re:classloading,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,pl:mixin:APP:structureessentials.mixins.json:LevelCreatedCallback,pl:mixin:APP:citadel.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:majruszlibrary-common.mixins.json:MixinMinecraftServer,pl:mixin:APP:mixins.essential.json:feature.sps.Mixin_IntegratedServerResourcePack,pl:mixin:APP:mixins.essential.json:server.MinecraftServerAccessor,pl:mixin:APP:mixins.essential.json:server.MinecraftServerMixin_PvPGameRule,pl:mixin:APP:mixins.essential.json:server.Mixin_ServerCoroutineScope,pl:mixin:APP:mixins.essential.json:server.Mixin_PublishServerStatusResponse,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetDifficulty,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetGameType,pl:mixin:A}
at net.minecraft.server.MinecraftServer.m_206580_(MinecraftServer.java:251) ~[client-1.20.1-20230612.114412-srg.jar%23488!/:?] {re:mixin,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,re:classloading,pl:accesstransformer:B,xf:fml:xaeroworldmap:xaero_wm_minecraftserver,xf:fml:xaerominimap:xaero_minecraftserver,pl:mixin:APP:structureessentials.mixins.json:LevelCreatedCallback,pl:mixin:APP:citadel.mixins.json:MinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:majruszlibrary-common.mixins.json:MixinMinecraftServer,pl:mixin:APP:mixins.essential.json:feature.sps.Mixin_IntegratedServerResourcePack,pl:mixin:APP:mixins.essential.json:server.MinecraftServerAccessor,pl:mixin:APP:mixins.essential.json:server.MinecraftServerMixin_PvPGameRule,pl:mixin:APP:mixins.essential.json:server.Mixin_ServerCoroutineScope,pl:mixin:APP:mixins.essential.json:server.Mixin_PublishServerStatusResponse,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetDifficulty,pl:mixin:APP:mixins.essential.json:server.integrated.Mixin_SetGameType,pl:mixin:A}
at java.lang.Thread.run(Thread.java:840) ~[?:?] {re:mixin}

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

Edited July 24Jul 24 by ryank5oo

Quote

Jul 24Jul 24 ryank5oo changed the title to Multiplayer Server (Essential Mod) Crashes randomly and often in The End (exception in server tick loopError)

July 24Jul 24

Same issue without cupboard?

Try my Modpack

>>Link to Curseforge<<

Quote

July 24Jul 24

Author

I'll try it without cupboard later tonight but i think its a dependency for something

Quote

July 24Jul 24

Author

It doesnt start without cupboard, is that the mod causing the crashing do you think?

Quote

July 25Jul 25

I am not sure - but it is mentioned

Try my Modpack

>>Link to Curseforge<<

Quote

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Multiplayer Server (Essential Mod) Crashes randomly and often in The End (exception in server tick loopError)

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