Internal Exception: java.util.ConcurrentModificationException

[QuantumXenon]

Versions: Origins (Forge) 1.10.0.1, Forge 47.1.0

Sometimes (but not every time), when I try to generate a new world, the game fails and shoes the error Internal Exception: java.util.ConcurrentModificationException.

Here is the part causing the issue from the logs:

[Netty Server IO #5/ERROR] [net.minecraft.network.Connection/]: Received class net.minecraft.network.protocol.game.ClientboundDisconnectPacket that couldn't be processed
java.lang.ClassCastException: class net.minecraft.server.network.ServerGamePacketListenerImpl cannot be cast to class net.minecraft.network.protocol.game.ClientGamePacketListener (net.minecraft.server.network.ServerGamePacketListenerImpl and net.minecraft.network.protocol.game.ClientGamePacketListener are in module minecraft@1.20.1 of loader 'TRANSFORMER' @781711b7)
	at net.minecraft.network.protocol.game.ClientboundDisconnectPacket.m_5797_(ClientboundDisconnectPacket.java:7) ~[client-1.20.1-20230612.114412-srg.jar%23166!/:?]
	at net.minecraft.network.Connection.m_129517_(Connection.java:174) ~[client-1.20.1-20230612.114412-srg.jar%23166!/:?]
	at net.minecraft.network.Connection.channelRead0(Connection.java:159) ~[client-1.20.1-20230612.114412-srg.jar%23166!/:?]
	at net.minecraft.network.Connection.channelRead0(Connection.java:50) ~[client-1.20.1-20230612.114412-srg.jar%23166!/:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.local.LocalChannel.readInbound(LocalChannel.java:299) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.local.LocalChannel.finishPeerRead0(LocalChannel.java:445) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.local.LocalChannel.access$400(LocalChannel.java:50) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.channel.local.LocalChannel$5.run(LocalChannel.java:403) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174) ~[netty-common-4.1.82.Final.jar%23123!/:4.1.82.Final]
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167) ~[netty-common-4.1.82.Final.jar%23123!/:4.1.82.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470) ~[netty-common-4.1.82.Final.jar%23123!/:4.1.82.Final]
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:569) ~[netty-transport-4.1.82.Final.jar%23128!/:4.1.82.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.82.Final.jar%23123!/:4.1.82.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.82.Final.jar%23123!/:4.1.82.Final]
	at java.lang.Thread.run(Thread.java:833) ~[?:?]

[MerchantPug]

Okay, this one should be fixed in both of the places it can be caused.