invalid player data, return to server list

[Icarus-Resolution]

Please confirm the following.

• I checked the existing issues for duplicate problems
• I have tried resolving the issue using the support portal
• I have ensured my Modrinth App installation is up to date

What version of the Modrinth App are you using?

Modrinth App 0.14.6

What operating systems are you seeing the problem on?

Windows

Describe the bug

when trying to join into a newly made or pre-exisiting single player world after everything is finished loading i am hit with an error message that says connection lost, invalid player data and promoted to return to server list despite not trying to join a server. while disabling certain mods does occasionally fix the issue it returns even when installing previously working mods.
i have logged out of both my Modrinth and Microsoft account as well as updating both minecraft and its launcher, deleted world files, and deleted server files.

Steps to reproduce

i have no godsdamned clue.
just make a new instances, install some mods, and try to join a single player world?

Expected behavior

i expected to join into my single player world and make sure everything was functioning with the modpack.

Additional context

issue began after creating a new instance