Mod Version:

DynamicSurroundings-1.12.2-3.6.0.2 (core mods in my pack use an older version of mixin than the latest 1.12.2 DynamicSurroundings build).

Forge Version:

14.23.5.2487

Link to client log:

https://pastebin.com/eZTe7rgL (shortened to just what happened after I joined the world, since the full log was too long for pastebin's size limit)

Link to crash log:

https://pastebin.com/BFQUyD62

Description:

I just added Dynamic Surroundings to my pack, and the game loaded fine, but crashed on the creation of a new world. My pack never crashes on world creation/join, so this is definitely tied to the addition of Dynamic Surroundings. I've also never seen Recurrent Complex or Ruins be listed as the culprit of a crash until this one, which is interesting.

I did notice that Recurrent Complex and Ruins both loaded multiple chunks to generate structures right before it crashed, so it could be tied to that.

I hate to be that guy, but this crash is indeed currently part of a private kitchen sink pack of 250 mods (on the nose). It's an RPG-themed pack, and I am intently developing it, tweaking configs, creating new structures, etc., and I am planning on releasing it to the public once it's been fully developed. But there's no available CurseForge page for the pack at the moment. I could drop a link to the modpack's .zip on DropBox, if that'd be helpful.

Unfortunately this has nothing to do with DS specifically. This crash happens during world gen on the server thread. Though DS does have a server side piece with 1.12.2, the logic has absolutely nothing to do with world gen. It could be that the addition of DS altered startup timing a bit which exposed this particular issue.