Before Continuing:

• Check you are using the latest version of the mods and its dependencies
• Always include a latest.log if you are crashing
• Remove mod that enhances Minecraft: Optifine, Sodium, others. The issue persists.
• If you are unsure which mod is the culprit.
  Disable all of your mods and enable them 1-2 mods each time to isolate the culprit
• Confirm that there is no existing issue with a similar description submitted in the list of issues.

Version

1.20.1-FABRIC

Supplementaries Version

supplementaires-1.20-3.0.4

Moonlight Lib Version

moonlight-fabric_1.20-2.13.21

Issue Detail

When leaving a world after gaining the slimed effect (whether it be by getting hit with a slime ball or taking damage from a large slime), and then later rejoining, you'll be met with an invalid player data screen, essentially locking players out of their world.

I have only tested this on fabric so far, but it could also be a problem on forge.

Should be fixed

indeed it is, ty!