Bathroom Floor leak - Cougar 280

[Streetwise]

I've got a 2003 Keystone Cougar 280 with the bathroom in the back and a garage beyond that. I've developed a leak underneath the baseboard "box" in the bathroom that houses the pex supply lines to the tub and toilet. I've peeled up the linoleum to expose the OSB sheeting to hopefully dry it out. It seems that its rain that is causing the wetness as the pex lines are not pressurized. The camper spent the winter with the front down, so that tells me that the water is getting in at the rear since it's not running forward. The garage seems to always be dry and last year, I took the trim off of the side of the camper where the fiberglass transitions to the metal skirt around the bottom. It seems that the factory does not caulk that, so many of the screws that hold the molding on were rusted right off along the entire edge of the camper! I caulked it and put new screws in, but still leaking. I've checked the roof, bath vent, running lights, etc but no luck. Is there a "typical" failure that I don't know about? We're planning to re-coat the roof in the next week or two. In the meantime, the camper has developed a smell... ugh.