Since you said "older" I'm assuming you have the traditional ball hinges. I don't understand how the cast metal body of the hinge could bend. That would require a lot of force. The center bolt through the ball and spring could be bent or worn. Those parts can be replaced (
www.campingtreasures.com, owner is a member here).
But a large gap at the bottom is often caused by deterioration of the internal wood core of the door (the thick part as you look from the inside), usually from water
leaks around the window, or (less likely) the door handle and/or hinge bolts. You can check by drilling several small holes into the bottom of the thick part on the inside of the door. Worst case, water will actually run out. You can also push a wire into the holes and feel for mushiness in the wood.
Aside from the gap at the bottom, how well does the top half of the door fit in the opening? From the outside, is the gap fairly even all around? Is the top level with the door opening?
The other thing to check out is the integrity of the frame around the door and forward on that side.
Let us know what your inspections turn up. Some good pictures would help. Include wide views to show the context as well as close-ups of problem areas.