OTG Mod for Forge
1.12.2 v9 from curseforge.com with latest biome bundle
forge 14.23.5.2847

Crash log with all mods:
https://pastebin.com/raw/J91regqb

Game crashes sometimes upon connecting to the server, starting the modpack and joining again helps.
Friend experiencing same problem with same error. So its propably not PC related.

Suggest updating your forge and optifine to the most recent versions and seeing if that helps, your optifine build is from 2018.

Tried, still same issue even with latest forge and optifine.
https://pastebin.com/raw/RxxChgi6

Tested without optifine, still crashes on newest forge.
https://pastebin.com/raw/tLr3gBGK

Maybe caused by bungeecord, fixed with dev build provided by Authvin.

Fix will be included with v9.3 release when it goes up on curseforge

Appears to be an issue with packets and timings, the client seems to be requesting data in the world before the connection was properly resolved and data processed. Will add a null check for 9.3, which should solve the immediate problem, hope this is not an indication of a more fundamental issue though. Will post a new dev version on the discord asap an post a link.