Unsure if it's RPGDifficulty, but I seem unable to crash the server after removing it.

I also had another type of crash that I attributed to Graveyard mod that seems to be opened in #24 . I didn't know that crash was related to having both mods installed, so that's nice to know.

This crash however was without Graveyard added.

Two logs. Identical errors. Only one mentions RPGDifficulties though:
crash-2022-06-21_01.09.47-server.txt
crash-2022-06-21_01.15.51-server.txt

Hope it helps, posted as requested from CF :)

Should now be fixed with 66b59f1
Actually not sure if it fixed it o.o

Flew around for a good 10 minutes without a crash. I can't state if it's guaranteed fixed or not.

Reopen if still happening with latest version :)