Pack Version:
b3d4ed5

Description:
Server crashed on a Lost Cities map when exploring underground, can't load the world anymore

Expected Behavior:
I expect it not to crash

Crash Log:
Attached
crash-2021-08-14_23.27.04-server.txt

This is very likely to be a corrupted world. The code in this area is from vanilla/Forge and is pretty much the lowest level of chunk access, where the region files are being read.

Was there a power failure/did your computer crash for some other reason recently?

I think you're right. I've restored the world from backup and it loads without issue. And no, my PC was working fine when the crash happened. The only odd thing that has started to occur recently is when I try to enter a world (especially with modded 1.12) is that Windows would suspend javaw.exe process and I have to resume it manually through Resource Monitor.