Riding death worms causes an updating entity crash. I think this is an old problem with I&F because it happened on the regular version as well. It's not a mod conflict as this has happened in two different modpacks and when I&F RoTn is installed by itself without anything else.

Using RoTn 1.9.1-1.1.2
Forge 14.23.5.2860

Crash report:
crash-2022-04-09_19.32.09-server.txt