The interior walls are just partitions, sort of tacked into place. When the RV travels on the road or gets leveled up on a campsite, the chassis (frame) gets twisted and shifted, pushing the sidewalls, roof and floor back & forth out of alignment with each other and various joints get stressed. Sometimes beyond their ability to recover. Ultra-light designs are more susceptible to this because structural rigidity gets compromised to reduce weight. None of that helps you with your problem, though.
You will need to push those panels back in place as best you can and figure out ways to re-attach them. Plus, check all the exterior joints as well, since there clearly has been a lot of movement. Chances are good that joints where the sidewalls come together with each other and the roof have also "worked", possibly breaking loose screws or rivets and stretching the caulk (sealant) that makes them watertite. You want to catch anything like that before it gets worse.
