Bug: Player stuck on "Joining..."; java.lang.IllegalArgumentException: Failed to serialize ResourceKey[aether:moa_type / aether:black]: Item must not be minecraft:air

[icycoba]

What Feature Types Apply to This Bug?

Entity

Other Type

No response

What Type of Bug Is This?

Annoyance

Mod Loader

NeoForge

Mod Loader Version

21.4.38

The Aether Version

1.21.1-1.5.1-beta.4

Is This Bug a Conflict With Another Mod?

No response

Client Log

https://gist.github.com/icycoba/71a982f1a44de0163e7d8f09eb38dca0

Crash Report (if applicable)

No response

Steps to Reproduce

The bug happens seemingly randomly on our server. The only way I could think to reproduce would be to be near (black) moas, either a pack of adult saddled or unhappy baby.

What You Expect To Happen

I expect to join a server other people are playing on.

What Actually Happened

I try to join a server, only to be left at a "Joining..." screen. When other people leave or try to join for the first time, they are stuck on loading too. Restarting server helps, until some (possibly unlogged) event happens that makes it impossible to join back into the game.

Additional Details

This bug doesn't seem to have any pattern at all. It just seems to happen after some time randomly. We have brought moas to overworld, we are incubating them there in caves and once they grow up, we bring them above the ground. The issues seem to have started after we brought them from the aether, however it may be due to something else that I don't see (because the log mentions black moa and nothing else).

I tried to kill them, restart the server and I'll comment back soon if anything changes.

Please Read and Confirm The Following

• I have confirmed this bug can be replicated without the use of Optifine.
• I have confirmed this bug is on the most recently supported version of Minecraft.
• I have confirmed the details provided in this report are concise as possible and does not contain vague information (ie. Versions are properly recorded, answers to questions are clear).
• I have confirmed this bug is unique and has not been reported already.
• If playing on a modpack, I have reported this bug to their issue tracker already.
• I have confirmed that I'm reporting a bug in The Aether I, not The Aether II.

[icycoba]

Killing the mobs seems to have "resolved" the issue, however I have not tested it yet in Aether dimension itself.