Hi,
H'mm, OK, I see that the door itself "looks" to be sprung or out of square with the door frame in the camper wall.
It looks like what I have seen this issue before, and it is not the physical door that had the problem.
Try this, and it will confirm if your door is square or if the door frame in the wall is out of square.
If you have a 24" carpenter or rafter square, with the door open, hold the square on the corners of the door. Across 24" an out-of-the-square door should jump out and scream the door is sagging. Granted, for the age, it might be 1/16" or maybe even 1/8" out of square in 24", but not the amount you show in your pic.
This is a 24" rafter square in case you do not know by the wording what
I am referring to. The only difference between a 24" rafter square and a 24" carpenter square is the rafter table of numbers in the middle.
If you do not have a 24" square, You can use a smaller one, too if that is all you have, then you can use a tape measure and measure diagonally across the corners of the open door. From the top right to the bottom left, measured diagonally and read the number. Then top left diagonal down to the bottom right and read the number. If the door is square, the numbers should be the same. If they are off 1/16", well, OK., but you are looking for something close to 1/2" out to match up with your pic
If you find the door is way out of the square, you can lift it on the bottom non-hinged corner with the door open (outside left side facing the camper door) and see if you can turn the door back into the square. The extruded aluminum framed doors are rigid and do not bend much. The older wooden framed ones fall out of a square from wood rot.
If your door comes out square or darn close to it with no lifting to make it square, then the camper wall has shifted out of square, and the door frame becomes out of square, which then looks just like your pic.
Have a look and see what you find, and report back. I want to avoid jumping into what can be wrong with the camper to make the door frame out of square until we know if it is the drop frame or the actual door itself. Out-of-square door frames in the camper wall have happened before, this is not a new problem.
I hope this helps.
John