The RV cover is a plastic of some sort. And like all plastics they dry out and deteriorate over time. The beating elements of nature, the sun especially, UV rays, all the harsh wind, constant exposure, literally degrades everything over time.
I owned my Outback for less than 3 months when the rubber cap on the black tank flusher (the strap) simply melted. I ended up getting a replacement and so far that one is ok. But the little cap on my satelite antenna and cable antenna hook up is now soft mush also.
At 3 months we took our Outback back to our dealer for a 3 month after purchase re-inspection and any warranty work. I did not catch it, but they did. All the screw holes on my plastic fenders, on both sides were broken out. They ordered new fenders and replaced them. So far, almost 2 years later now, they have not broken out again.
Plastics do need special attention, and replaced often, even if they still look OK, they may be brittle or mush.
In my Springdale, the bathroom vent fan broke a blade (plastic). When I attempted to replace the fan, the other blades simply crumbled in my hands. Got the fan blades and motor replaced (it failed after 7 years), and all was well again.
Yes, I do inspect the plastics on my camper, quite often. I wonder about those plastic covers over the propane tanks? They are already loosing their color. Before they fall apart, I'll replace.
Wise advise. Check often!