It seems that whenever I fight spiders, my Minecraft crashes. I've been able to track it down to when I get the advancement for getting stuck in messy cobwebs, which would explain the problem.

If I try to rejoin with Lithium it states its a lithium error, otherwise it says 'Network Protocol Error'

Note: I am playing with a large modpack, so it might be a compatibility issue but I'm not sure myself.

Stuff:
logs and specifications.txt