Outside window caulking?

I would love to see what you are seeing, and referring to as caulking. If the windows have been gone-around with caulk or silicone, it can be a pain to remove, but getting rid of it is the best alternative.
Most...yeah, I'll say most (less committal and more scientific than saying "all" or "always") Most campers were built with a putty tape around all the openings; windows, doors, vents roof vents, j-rails, and cargo doors as well. Over time the tape dries and hardens and loses its "grip" on the aluminum of the siding and the framing. This will always cause leaks...unless it had been kept under cover for all those years. Lots of owners have been known to "cure" the leaks with caulking of some sort, mostly silicone (miracle-cure that it is perceived to be...), globbed on heavily around the exterior of the frames. Roof coating or tar is sometimes the go-to for the roof vents, which is another problem but based on the same premise.





The one I am finishing with this year was under a shelter for several years of its life. That kept the water out, but it does not stop the seals from drying out and going through temperature-change cycles. For the best expected results, I removed everything, a little at a time, and cleaned all the old residue off from the frames and siding, and replaced the putty tape.

Be advised there is a difference between "putty tape" and "butyl tape".  The differences are described in several places, and you may want to research that aspect a little too.