Ladder Top Mount Not Sealed
PrimeTime owners, I suggest you have a look at the place where your ladder is attached to the roof of your RV. I get the impression that they install all of the roof components (air vents, plumbing vents, skylights) and seal them before they attach the ladder, and then don't think to seal that roof connection afterward.
On mine, while there is the gummy gasket under the flange, I don't see anything that is going to stop rainwater from seeping down along the screws into the roof. On mine I see some slight bubbling of the roof in that area. I hope all of you find lots of Dicor Lap Sealant covering yours.