https://gist.githubusercontent.com/natanfudge/680f0ee920a405694b99f64bf4124eb7/raw/25dcfe210b6bd2f87d2cde1a9faac2428192ba6a/crash.txt

I sincerely apologize for the impulsive issue title.

It appears as that me.steven.mobsmainmenu.client.DummyClientPlayerEntity is the issue because NotEnoughAnimations tries to check rather the dummy player is climbing right now, and in the main menu there is no minecraft:climbable tag(or even world for that matter). I'll look into how this can be fixed.