Some units have a remote sensor for temp sensing. They can get dirty with dust etc. If you have one it would look like a plastic round type piece about the size of a quarter with a grill of sorts. They put them up high under cabinets, on a wall etc. Maybe in the end of the living area.
If no remote, check the sensor on the thermostat. It may be in use and dirty.
It may just be the location of the sensor is not optimum for the trailer.
Also, the sensor can be by a window where the sun comes in making it not allow the heat to come on when its cold in the coach until its too cold. Or the opposite stay on too long if near a cold window. A light turned on next to it can effect it as well. Both of these effect one of ours.
Just a few things for ya to check.