Find your 'thermistor'.........it should be in a plastic clip attached to the right hand fin in food section.

It has probably fallen down and is laying in bottom of food section.
The 'thermistor' is the temperature sensor that controls the cycling of fridge (electric or propane).
If it falls down off of fin then fridge cools and cools and cools regardless of what temp setting you use.
RV Tech should have put it back in place.
And a fan inside to circulate the air does help even out the cooling areas in food section