I don't know what the fix is, but I do know the temperature setting on thermostats are not always as reliable as we may hope they are. We have all electric heat in our house, and every room has it's own thermostat. Right beside the thermostats in every room, I hung the same small thermometer in every room. And I find found it interesting that no two rooms matched the temperature setting on the thermostat with the attached wall mounted thermometer. So, "Kentucky Windage" prevailed in room. I marked all the termostats where 70 degrees was on the thermostat, when compared to the thermometer.
In all my travel trailers, I have never relied on the temperature shown or the temperature set on the thermostat. I keep a small thermometer right beside the thermostat so I know what is really happening. Now, I can usually get the temperature exactly what I want at the thermostat, but the rest of the trailer is all over the charts. From front to back, and depending on Summer or Winter, and depending on the upper level (fifth wheel), or the bottom level, no two places in the camper are EVER the same. So, in the end, it doesn't matter what the actual temperature is, it boils down to if we are comfortable or not. Who cares what the thermostat is set at.
2019 Montana High Country 375FL Fifth Wheel
2014 Chevy Duramax HD 6.6 - 3500 Diesel Dully Long bed Crew Cab