What's the issue you encountered?

While working on the 1.21.1 port of Aeroblender, I joined a world and began exploring the Aether when I crashed.
Looking into the logs I see there's a structure that doesn't load correctly and began investigating the issue.
I then understood that with all probability the issue isn't with Aether but rather with Terrablender itself.
After some testing I can see that there's an issue with the BiomeManager#getBiome method and other stuff.

How can the issue be reproduced?

• Run a Minecraft Instance with Terrablender and Aether 1.21.1 (CircleCi builds on their github)
• Enter a world and generate the "Gold Dungeon" from Aether.

Logs

https://gist.github.com/darksonic300/8b7ad827485730d687cbb14886608a9a

Mod Version

4.1.0.3

Additional information

I'm sure this isn't just Aether related, so there might be other mods that have the same issue.