Got up to clean top of caravan and saw a puddle at rear off side of the roof. It has been there since buying it . A quantity of water is slopped toward a joint between the rear and roof portion . Have had no damp in that area inside . My thought are is it possible to drill hole in side to inject a foam filler to pop it up?. In the past when up there the water had gone brown with probably tree s nearby and had to use several polishes to get rid of the stain .