We apparently faced this when we started to setup our quests. We don't know the exact reason for it, but for some reason, when mob quests are added and I try to fulfill them, the game throws an error + mobs don't drop anything besides exp.

https://paste.dimdev.org/lilefijube.mccrash
https://paste.dimdev.org/aqahozosuz.mccrash

Does anyone have an idea?

Can't find the issue on the latest version, and it appears that the links no longer work. The issue might've been fixed since then. Is this the case?

It is a bug on our side. THank you for reporting