Did you "Google" for the term: How do I clean a slot loading DVD player?
There are several "how to videos" as well as a number of "DVD Techie sites" with instructions on how to clean your DVD player. While none may work, some seem fairly easy for a RV owner to try. Might be worth a try. To me, the easiest was one of the first links:
https://lifehacker.com/clean-your-la...edi-1546763763
A simple "thin cotton cloth strip wrapped around a credit card, inserted into the slot to "wipe the lens clean"....
Might be worth a try to "Google" for an answer......