Just asking, did he check the screws on the roof? We had some under slide in bedroom over torqued and had to caulk. Check light area also, every light; last 5th wheel had a tiny, tiny pin hole around a safety light on side of trailer, caused wall damage (took 7 of 10 yrs ownership to find leak).
. But it only takes a pin hole to make somethink wet. Hope they find it soon and begin enjoying DT.