I pulled into the campgrounds the other day and when I stopped the door flew open. I had just drove 20 miles and never noticed anything in the mirrors, however I would of had to be turning left or braking and looking in the left mirror at the same time to see it happen. I checked the door and hinges and they were good but I found the striker plate to be loose. It is held in place by two rivets and two machine screws. The rivets had pulled loose and allowed the striker to move when closing the door.
The following photos show how I fixed and reinforced it.
Photo #2 shows the inside of the closetPhoto 3
The bracket and back-up plate I got at a hardware store. The last photo shows that the catch is fully deployed onto the strike plate. The oak flat helps to transfer the force when closing the door over a larger area.
It is overkill, the way I like things to be.