Modpack version
1.58

Can the issue be reproduced?
Yes

Logs
crash report

Issue
I've had numerous hangs while exploring the Twilight Forest in single player, usually near hollow hills. I originally thought I was just running into out-of-memory issues, but after killing the client on the most recent one, I noticed in the logs that the server was actually crashing with an error relating to swarm spiders (see pastebin link above for full crash report):

Description: Exception ticking world
 
java.lang.BootstrapMethodError: java.lang.IllegalAccessError: Class 'twilightforest.entity.EntityTFSwarmSpider' no access to: class 'net.minecraft.entity.ai.EntityAITasks$EntityAITaskEntry'

This issue is caused by the Java you're using. Switching to standard JRE fixes it.