Your unit is not that old. Try removing any caulk that is on it now, and after cleaning, tape with painters tape, apply a fresh sikoflex or other caulk.
Dave, I have the original service record work that was performed on my coach, and I wish they would have followed your suggestion on taping off at Jackson center where previous owner had it replaced. Terribly sloppy work, I would have never accepted it. Only good thing about it is that it doesn't leak.