Hello Patrick,
The Lock Assembly is held in place by 3 screws and not adjustable. Make sure it's screwed in tight. Hammering won't fix anything.
The Lock Plate is adjustable. Remove the lock plate and make sure there are no shims behind it. If so, remove, most likely problem solved. If no shims, look to see if any are under the 2 door hinges. Possibility the rear door is too close to the rear wing. If no shims and you can't move the door forward at all, then an extreme fix may be grinding the back of the lock plate to make it thinner.
As a side note, the steel dowel was once round. It can get flattened at the point of contact with the lock assembly latch. Remove the lock plate and you'll find on the back you can loosen the screw to the dowel, rotate the dowel so the round part is where it needs to be. Tighten the screw, good to go.
Once you figure out what the problem was, it's time to align the lock plate. It's adjustable, up/down right/left. To confirm it's in it's correct place, roll the window down so it doesn't come in contact with the rubber seal, hold the door handle button in so it doesn't latch and close the door. It should close easy with no resistance (except for the rubber seals around the side/bottom of the door. To confirm it's good, close the door. Did it close completely and the body line and door/wing line up? Good. Now gently push the handle button enough for the safety catch to stop the door from opening completely. Door should still be closed but not totally closed. Push the button more for it to completely open. Confirm the safety latch works. (The latch has 2 cut outs, safety and closed).
Let us know your findings.
Good luck.