We are all about to get destroyed by Irishdomer so I wouldn’t worry to much about it
So, to move to a place you have to leave an assistant there, or pick up an assistant that’s already there. It’s a way of making you think about how you move around the board. You should definitely be able to perform the cards action if you’re moving onto an assistant that’s already there.
I can only think with the jail thing was perhaps they were already on the jail card? After I finish a cards main action I get a pop up if I can send someone back to jail.