ISSUES NOT USING OUR TEMPLATE WILL NOT BE CONSIDERED AND WILL BE CLOSED!

Describe the crash
i was mining down in the overworld and it said "shutting down internal server" and kicked me out of my world
also happened when i was flying in creative mode on a different world.
it only happens after some time has passed.

To Reproduce
Steps to reproduce the behavior:
?????
Crash Log
Click "Get Link" from the crash and paste it here. Or post the log if it's a server.
https://paste.dimdev.org/edamabahed.mccrash

Info (please complete the following information):

• Modpack Version: 2.76.2
• Server or Singleplayer: singleplayer
• Version the world was created on: 2.76.2

Additional context
pepega clap world record

Entity's Vehicle: ~~ERROR~~ NullPointerException: null

I'm thinking a Zotsypre or another entity was on top of a skeleton warrior. Or a skeleton warrior tried to hop on top of another mob and that caused a crash. We'll remove skeleton warriors using others as vehicles, if its not already disabled. @SandwichHorror