If you're measuring voltage at a wall outlet, most likely it is the cord, the wiring between the cord and the breaker box, the plug, or the connection in the breaker box (or the main breaker itself) in your camper. The problem is across separate circuits which pretty much eliminates individual breakers as long as the voltage remains steady at the pedistal. Look hard for copper wiring that is turning brownish or wire insulation that looks like it's melting, it sounds like a bad connection someplace.
2004 Wildcat 28BH
2012 Ram 2500 CCSB 6.7CTD