I had the exact same problem with my 1981 Casita
. Took it to the Scamp dealer (Minnesota is much closer to me than Casita
in Texas.) They found that the support inside the hinge side of the door was inadequate. My camper had been refurbished before I got it, so I don't know what it was like before. BUT basically, the service guy opened the door, and kind of pulled it in and out and you could SEE the fiberglass flex in that area. So it was less of a straight up & down (side) opening; but had gradually taken on more of an additional slight curve as it had settled over time. (Greater than the intended curve.) Simple fix was to add a beefier reinforcement inside the door frame on the hinge side, forcing it to be more 'upright' again. Think of it this way: added weight
, roof AC, etc seems to compress old fiberglass shell slightly so the door curve was no longer the same as the body curve.
I had originally left it alone since no rain came in, but one time a bird found a way in (& back out!), if not for bird poo all over I'd have never known it was there. It's definitely an easy access for mosquitoes! (Chipmunks, snakes, squirrels?)
I was surprised & relieved by the fix because I thought my whole door would have to be removed & reshaped, not so I'm my case! Hope your fix is so simple! I had newer hinges already, something else to consider while you're at it. Happy camping!