Is it with just that movie or all movies?
If just that movie it is most likely a scratched DVD.
If all movies it might be:
1) overheated read laser - try a fan to blow heat away from the unit.
2) humidity in the camper - Let the unit run for a few hours to warm it up enough to cook out any water vapor.
3) bad DVD player circuitry.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW