I don't know about your particular car but some vent wings have a little flat metal piece on the bottom strut that keeps the vent from opening too far.  If one opens the vent about half way, the metal piece is parallel to the opening and will slide right out

Sorry - posted this in the General Discussion section and didn't know how to delete it.  But it probably belongs here.  TIA for any help.

OK, what's the trick for getting the door window frame off my P6 BC?  I have the four screws out and the frame is loose.  But the vent wing lower pivot hangs up when I try to pull it out of the door.