How to reproduce:

1. Install this mod, fabric api 0.37.0 and starlight 1.0.0-RC3 (https://github.com/Tuinity/Starlight/releases)
2. Make a new creative world and switch to spectator
3. Fly around at full speed until worldgen stops and the server freezes

Oh wait, this freeze is also possible to reproduce without starlight, but starlight does make it a lot easier to reproduce.

I think the best way to reproduce this bug is to install starlight or set your render distance to 32 and fly around.

It's possible that this is deadlock in the biome map cache. I'm taking a look into this.

It might also be worth checking if the latest version (0.4.0.3) solves this. It's possible this is related to structures. Version 0.4.0.3 contains a structure-related fix, and your screenshot contains the beginning of a village.

still happens on 0.4.0.3

Can confirm the existence of this.