Describe the bug
It is not possible to generate a new world, loading is stuck at 0%. Previously generated worlds load without problems. I tried to turn off other mods that affect the generation and loading of the world, but without success.

To Reproduce

1. Create new world
2. Stuck on loading screen
3. Closing the game

Expected behavior
I expected the world to generate

Screenshots
https://i.imgur.com/f84Akf0.png

Runtime info (please complete the following information):

• OS: Win 11
• Minecraft version: 1.21.4
• Mod version: 3.1.2
• Mod branch: -

Crash reports / logs
https://pastebin.com/1D54LGd3

Other mods
https://pastebin.com/1D54LGd3

Checklist

• I am using the official version of the mod.
• I tried the latest development version but the issue persists.
• I searched for similar open issues and could not find an existing bug report on this.

Additional context
maybe this issue caused by my brainrot modpack

Try finding the minimum set of mods reproducible.

So, the mod conflicts with flashback, and the flashback mod conflicts with everything in the modpack. You seem to find a conflicting mod, but after game restart, it is already innocent. A clean modpack with no extra mods is working fine.

Flashback destroyed this method call needed for consistency. This should be fixed on their end.
https://github.com/Moulberry/Flashback/blob/53980aaf06e01d8598afa126e4bd01e0b3fa398c/src/main/java/com/moulberry/flashback/mixin/replay_server/MixinServerLevel.java#L72

Or install ModernFix

It thinks the biome "the_end" is an unbound value for some reason, which it is not

I have this problem, but only when trying to load the end dimension. Really strange

And i think it's fine in worlds that had the end already loaded, but i'm not 100% sure