I just learned this from a friend who first learned it from Steve and Michelle Cook.
The "bolt" for lack of a better description that protrudes from the aft side of the door jamb should move up and down about 3/8ths of an inch. If yours is stuck, spray some Jigaloo or WD-40 or Corrosion-X behind the lalge washer and keep working it up and down. Once it moves, your door will close much tighter without slamming.
In the photo, the distance between the top of the washer and the blue tape is the distance the stud moves on our coach. Since the lubrication is behind the round washer, you don't have to worry about it rubbing off on your clothes. Now if I can just figure out how to not catch a short sleeve in it.