When trying to enter the world in versions above 4.0.3, it gives an "Invalid Player Data" error and does not join the world.

Logs: https://mclo.gs/UgwSoq5

Please try this jar and make sure to test on new world only. If this doesn't solve the issue I will check again when I'm home.

https://www.dropbox.com/scl/fi/sr8ahb2jfnbw5d0fzgt9h/fish_of_thieves-mc1.21.1-v4.1.2-neoforge.jar?rlkey=4e2cgsgm9ic3vsmbm80crw6w0&st=n6cxjr1r&dl=0

I tried it and it gives me another error when creating a new world: Internal Exception: io.netty.handler.codec.EncoderException: Failed to encode packet 'clientbound/minecraft:update_recipes'

Logs: https://mclo.gs/grjaBQx

I don't think its come from my mod now, did you try disable fish of thieves and the issue still occur?

I don't think its come from my mod now, did you try disable fish of thieves and the issue still occur?

I tried to disable Fish of Thieves, and the world was created perfectly. Maybe it can be related to https://bugs.mojang.com/browse/MC/issues/MC-258971

Can you try debug with binary test? Removing mods in the half and test it over and over. Due to my time is limited with fulltime job.

Only thing I see in the log is Caused by: io.netty.handler.codec.EncoderException: Empty ItemStack not allowed which I'm not sure it's really from FoT. Maybe some mods break the recipe packet?

Yeah, it can be. Ok I will try it and hopefully find the conflict.

I'm closing the issue according to the new update. If I find the conflict I will open a new issue. I appreciate your help!

Np!