I had opened up the port 7777 and then we got going and had a good time.
I was the one who always hosted the game and when we completed we both hit the "adveture+" button deleting our progress from before.
Now i read that certain things don't save if you join a game so i was wondering if this is the conflict we are now encountering which results in my partner now crashing to desktop during the loading screen past the negotiate lobby and just before we enter ingame.
I did have one special feature unlock enabled, big head mode

I don't know know if this is my end or their end which needs to be fixed, i assume their end as they have the crash to desktop.
Has anyone got any ideas about a fix?