Water leaks can be hard to find at times. It could even be your clearance lights, antennas and it could be where your awning attaches to the side wall. There is some caulking on the top where it attaches if I recall.
Caulking is really not all that great on the roofs of a lot of coaches. That is why a lot of RVers decide to Eternabond the whole thing if you have any seams on top where the front cap and rear caps attach to the top roof piece. You could have a leak in the front, but will go to the area of least resistance.