Minecraft Version

1.20.1

What happened?

This isn't causing any bugs, but I believe this may be the cause of the Invalid Playerdata when trying to join a world for the first time.

How do you trigger this bug?

1. Create a world
2. Join world
3. Save and exit world
4. Attempt to rejoin
5. Get kicked for invalid data
6. Attempt to join again
7. Success

Loader

Forge

Loader Version

1.20.1-47.2.21

Mod Version

5.7.2-1.20.1

Relevant Log Outputs

Latest.log
Debug.log

Does this happen with only Curios loaded?

I also noticed that you have Sinytra Connector installed, does this happen if you remove it?

Are either of you running Sinytra Connector as well?

I am not

I am getting this same issue when trying to run the latest version of Beans Backpacks.

I get the same issue but mine just full on crashes the server, this is the beginning of a very long crash log, for me it crashes with elytra slot enabled, if its disabled it works fine:

[ne.mi.ev.EventBus/EVENTBUS]: Exception caught during firing event: Duplicate Capability Key: curios:item com.illusivesoulworks.elytraslot.ElytraSlotForgeMod$1@30e36fc9

Usually this is a result of multiple mods trying to add the same capability to an item. My suggestion is to try and remove mods in order to isolate which ones are conflicting with each other. In addition, it may be beneficial to begin with a bare minimum environment with just Curios API and a couple other mods to verify if it's a Curios bug.