I've had problems with my front vent ever since buying my Airstream. It's a '73 Tradewind. Three dealers have worked on it, it only worked right after one of them did their magic.
I am including three photos here.
The vent cap won't shut. I am including three photos--two with it in the open position one with it "shut." The shut photo is deceptive because it looks like one edge is actually shut, however, the back edge is open so far that the whole thing "rocks" open and catches wind while driving.
I used duct tape to shut it for a while but want to fix it properly.
This is as far as it will "shut" currently. It actually rocks open, so the side that looks shut does not stay down either.