Can confirm it's a bug that happens when Trailier Tale's Catacombs structure attempts to generate. When this occurs, worldgen freezes and the world bricks, so you have to restart the game / world. The logs and crash reports should provide enough information as they seem pretty explicit about the problem in this case. Not sure if it's c2me or TT which needs to fix it, but I can confirm that the problem is not present when they aren't used together.

You'll find the c2me warning near the end of the log, and the reference to the catacombs causing the crash in the crash report.

latest.log

crash-2025-01-31_20.47.37-server.txt

It's more likely a frozenlib issue and needs to be fixed on their side.

The easiest way to do so is probably to make these two methods synchronized:
https://github.com/FrozenBlock/FrozenLib/blob/8c36dd7d9fc5ac8828c4613529803688ce6accc6/src/main/java/net/frozenblock/lib/worldgen/structure/mixin/StructureTemplateMixin.java#L36

Would this slow down performance at all?

It shouldn't slow things down without the presence of C2ME, as there's only one thread touching this and nothing will ever be waiting for the lock.
With C2ME, this should be good enough as long as settings::addProcessor is reasonably fast.

It's more likely a frozenlib issue and needs to be fixed on their side.

The easiest way to do so is probably to make these two methods synchronized: https://github.com/FrozenBlock/FrozenLib/blob/8c36dd7d9fc5ac8828c4613529803688ce6accc6/src/main/java/net/frozenblock/lib/worldgen/structure/mixin/StructureTemplateMixin.java#L36

Would this slow down performance at all?

All it does it just add values in a list to the structure’s processor list. I’d assume it’s fast, then.

Just implemented your suggestion!