Minecraft Network Protocol Error Report - IndexOutOfBoundsException in NonNullList

Overview

While using the All the Mods 10 (ATM10) modpack, the Minecraft client encountered a java.lang.IndexOutOfBoundsException, leading to a disconnection and generation of this error report. The exception occurred during packet handling when trying to access index 122 of a list with length 122.

Environment Information

• Minecraft Version: 1.21.1
• Mod Loader: NeoForge 21.1.116
• Operating System: Windows 11 (amd64) version 10.0
• Java Version: 21.0.3, Microsoft
• Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Microsoft
• Memory Allocation: Initial 512 MiB, Maximum 8064 MiB
• CPU Information:
  • Model: 11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz
  • Physical Cores: 8
  • Logical Cores: 16
• Graphics Card Information:
  • Name: NVIDIA GeForce RTX 3050 Ti Laptop GPU
  • VRAM: 4096 MiB

Error Details

• Time: 2025-02-17 22:50:53
• Description: Packet handling error
• Exception Type: java.lang.IndexOutOfBoundsException
• Exception Message: Index 122 out of bounds for length 122

Crash Log Summary

---- Minecraft Network Protocol Error Report ----
// Maybe a shark bit some cable

Time: 2025-02-17 22:50:53
Description: Packet handling error

java.lang.IndexOutOfBoundsException: Index 122 out of bounds for length 122
	at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)
	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
	at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
	at java.base/java.util.Objects.checkIndex(Objects.java:385)
	at java.base/java.util.ArrayList.get(ArrayList.java:427)
	at TRANSFORMER/[email protected]/net.minecraft.core.NonNullList.get(NonNullList.java:66)
	at TRANSFORMER/[email protected]/net.minecraft.world.inventory.AbstractContainerMenu.getSlot(AbstractContainerMenu.java:279)
	at TRANSFORMER/[email protected]+1.21.1/io.wispforest.accessories.menu.variants.AccessoriesExperimentalMenu.initializeContents(AccessoriesExperimentalMenu.java:494)
	at TRANSFORMER/[email protected]/net.minecraft.client.multiplayer.ClientPacketListener.handleContainerContent(ClientPacketListener.java:1291)
Possible Causes
Packet Inconsistency: The server might have sent a packet containing more slots than expected by the client.
Mod Conflict: Certain mods may have modified container behavior or structure, causing issues when parsing packets. Notably, the accessories mod seems to be involved as it triggered the exception while processing container contents.
Version Compatibility Issues: Some mods or coremods (like NeoForge) may not be fully compatible with the current Minecraft version (1.21.1).

Additional Information
Crash Report UUID: 93437043-9f6a-40b5-b4cc-2f2048952ae5

So the client and the server have the mods and the user is just unable to open any screen?

It is for single-user usage, not involving the server side

I can normally open the mod interface when I first load the save file, but after playing for some time, I can no longer open it. I need to restart the game to restore the functionality.

Does this happen when using the original Accessories screen instead of the experimental one?

Thanks. It looks good for now, but I'll keep an eye on it.

I tried switching to the original Accessories screen, but it still leads to a crash. It seems that the issue persists whether using the original or the experimental screen. Thanks for your help!

Both the server and client are using accessories correct with the compat layers if needed?

Like the issue seems to be a desync between the server and client on how many slots the accessories screens will have which is quite odd. Any consistent and minimal mod set would be appreciated to debug this issue

Commenting to say I have a player on a cobblemon server of mine that got the same type of crash. https://mclo.gs/ie1RVkA

Player said they tried using both the experimental and original screen, both resulting in the crash.
We have curios 9.2.2, accessories 1.1.0-beta.28, and accessorify 1.3.3