When loaded into a world:

When in the main menu:

It works fine if there are no other mods apart from eg Subtle Effects, Fzzy Config and basic things like Sodium are installed. But in my modpack with over 250 mods something causes this issue. So I wanted to ask if there are any known incompatible mods that could cause this behaviour while I try disabling mods and checking if it works, since that will take a while with this many mods, even when doing a "binary search".

I'm closing this for now, as it doesn't seem directly related to Fzzy Config. If you find out more, please feel free to add on to the closed issue, or reopen an issue if you think it's necessary.

That is very strange behavior. Unfortunately I don't know of any incompatible mods that would cause it. If you find out, please report back so an issue can be raised with the offending mod and I can know going forward!

This seems to potentially be some kind of multi-mod conflict or something. I have been re-making the modpack from scratch, adding a handful of mods at a time. When I got to Immersive Aircraft I noticed that the config screens broke again. Once I disable Immersive Aircraft it works again. But now comes the annoying part, if I make a new pack with just Subtle Effects, FzzyConfig, Kotlin for Forge and Immersive Aircraft I can't reproduce the issue.