When Pressing r on the keyboard in version 5.4 of the mod to open the GUI, the game crashed. Was in a modpack with several other mods, but none overwrite the keybind. Also, changes to musictriggers.json were recently made, but the crash still happened even after undoing them.
Crash report: https://pastebin.com/JGLxmq7m

Which MC version are you running?

Forge 1.16.5. There was an issue with my json, but even after I fixed it the crash still happens. I’ve also ran it with other (different) mods on a separate instance of Minecraft and it works fine there.

I will leave this open until 6.0 comes out just in case someone else has the same issue and can provide more information

For some reason, it seems to work now. Accidentally hit the key and it brought up the menu and didn't crash the game. I didn't change anything at all as far as I know. Weird.

I think I figured it out. It only seems to happen with MultiMC. On curseforge or any other launcher that I've tested, it seems to work fine.

The gui was overhauled so this should not be an issue anymore. Feel free to open a separate issue if you continue to have problems