One all-too-common problem is that something is heating the thermostat, so that it never properly reflects the room temperature. One coach we had placed both the thermostats adjacent to halogen lamps, so whenever the light was o the thermostat never cooled off. In a different RV, one thermostat was on an exterior wall and stayed warm whenever the sun was beating down on that side.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC