What happened?

Leak left unrepaired for long enough that the wood floor and horizontal brace rotted. Brace is the plywood you are seeing runs left to right on edge, it should go from inside frame (rusty tube on left) to wall at bottom of door on right. This would normally all be covered by front couch, but missing attachment point was allowing door frame to be out of square. Hinge side moved up, door hung crooked. Me fix.

The green fiberglass "corner" should have been helping to hold the wall and the floor in place, as well as that plywood brace.

Little leak, left long enough = major headache but then the camper is 37 years old.