One of my players is using the tweakeroo mod and in free camera mode, they are able to essentially attempt to sit on their own shoulder as an inchling. This effectively crashes the server - not sure if this is something that's fixable on this end or on another mod's one, or if the solution would just be "don't do that again".
Crash report: https://pastebin.com/6bTMnGjR
Using mod version extraorigins-1.18-7.jar

I've added a check to make sure the player can't mount themselves, but I'd also see if tweakeroo disabled mounting in general in free cam mode since that should be disabled imo