I had a water problem on my camper. i could not find any places that water could be coming in until I removed the rubber strip along the gutter rail and found that a large number of the screws were rusty and loose. its seems that water was wicking into these loose screw holes and seeping down into the wall. after a heavy rain I would discover water stains on the door sill, the window sills and any where there was an opening in the wall. I eventually replaced all the screws in the strips with stainless screws,applied caulk to them when i replaced them and made sure the screws were tightened sufficiently. end result, stopped all the water leaks.