Steps to Reproduce the Bug

Hold CTRL and press the Wrench icon

Expected Behavior

It should activate cheat mode

Actual Behavior

The game crashes and sends me to the multiplayer server list from Singleplayer (Error: Network Protocol Error)

Mod Pack URL (Optional)

No response

Mod Pack Version (Optional)

1.21

Extra Notes (Optional)

No response

latest.log

https://gist.github.com/TheEpicGamer1998/de36efc5860c8b2d68218c9815e04d22

This has been fixed and will be released in the next version (should be available in 20 minutes or so).

Thanks for the report!
I was able to reproduce this bug, I will try to figure out why it's breaking.
This seems to work fine on Fabric and NeoForge.