The door seal was basically a square strip of foam rubber except around the door latch, where there was a "flap" that stuck out. As far as the seal was concerned the door was 2 dimensional except at that kink at the belt line. The seal basically sits in the groove with a few spots of adhesive holding it in at the corners except at the door latch. You really had to glue the seal in hard at that point because of the change of direction. If it came out much at all the flap would show.
Also, VW's door mounts were notoriously flimsy, so the door could get out of alignment very easily. The door usually moved forward, which left a lot of room for the seal to escape.
