If you can, get a mirror and check all of the welds where your fifth wheel pin box attaches to the main frame. There shouldn't be any issues, but that would eliminate the worst possibility.
The flooring issue may be that they just didn't do it properly to begin with, and now all of the bouncing and flexing are causing a recurring problem. Same for the trim piece that keeps falling off.
I cannot imagine what it must be like inside the camper when going over some of these goat paths they call 'roads' these days. I'd be scared to actually ride inside my camper, I might never pull it again!