When my TT had this problem I did a temporary fix by adding a couple of self starting screws with washers to the aluminum framing on the outside of the door.
Then I used a couple of really light cables under the washers and around the screws.
I made the cable from each side into a loop and used some cable clamps to keep the loop together.
In the middle of the door, between of the loops, I added a screw eye.
I then ran the looped cables through the loops of the screw eye.
(Kinda hard to explain and I apologize for not explaing it better.)
By tightening down the screw eye I am pulling the sides of the door back together.
My temporary fix is going on it's 6 year. lol
But, then again I'm a Caveman.
( My original plan was to add L shaped brackets to the corners of the door after I pulled it all back together with the screw eyes. But, it worked so well I never added the brackets. If it gets any looser I can just turn the screw eyes some more)
It really doesn't look to bad no one ever notices it.
On rare occasions being a Caveman has it's advantages.