Looks like someone did some home made rehab on the vent mechanism. Do as marko39 says and then spray all the mechanical parts of the vent with WD-40 or PB Blaster to free things up. Previous owner may have tightened all the movable opening parts tight so vent couldn't be opened. It looks like someone tried to seal the vent closed. If the 39 vent mechanism is the same as the 40, I can send post photos of how it looks originally from the factory..
Appears the vertical portion of the door is bent and interfering with the screen. It should have been bolted to the hinge in four places and is not. I also suggest you take the inside portion apart to see if you can get it straightened out. The screen already has a hole in it so don't be afraid of damaging it since it is reproduced and common to the 40