Ideas that may not be of any value:
water does not flow uphill, so anything from below has to be a burst pipe spraying a lot of water upward that you should hear and most likely hear and see in the main belly storage area.
My guess is a loose fitting on the water line feeding into the toilet, or the toilet flush valve itself. Those valves are replaceable. Either way Fresh water leaks onto bathroom linoleum and seeps under the wall separating the bedroom from bathroom.
another but less likely source is the fittings for the washer dryer in the closet, or a bumped open valve there if there is no washing machine. The wood floor in that closet should be obviously wet and probably the carpet directly in front as well.
not likely a roof leak in that area, but that is where the roof changes slope. There are metal trim parts on the roof that hold down the plywood angle and the screws that hold it down need caulking every so often.
you don’t say where you are. If in an area of high humidity and you are running the air conditioner with the doors or windows open a lot, condensation can form in the vents and drip out of the ceiling ac vents.
as you track down the source you need to track where the water ultimately drains downward to. You need to dry the area out thoroughly with fans and perhaps a small heater or mold will take over, even in the desert. Given the area, I would remove one or more of the thin black panels on the back wall of the main belly storage area and dry with fan as needed. Ultimately the water will find its way into the fiberglass insulation under the 5er. If a lot has accumulated, you can feel how heavy the black fabric that lines the bevy is in that area versus areas forward or rearward from the leak. That belly fabric is removable. Just upen air with a fan may allow the insulation to dry, but if really soaked you can always pull it out and dry it on a sunny picnic table. I had to do that when I overfilled the fresh water holding tank a lot because I forgot.
good luck
JohnD222
Based in Florida except summer
2013 36FWS Lifestyle (our great 2010 Cameo 36FWS has happy owners)