If things in the refrigerator compartment are freezing, that problem is not a lack of propane.
The thermistor is a temperature-sensitive resistor which turns off the cooling unit when the refrigerator section is cool enough. If it fails, cooling stays on, things freeze.
In the back of the refrigerator (not freezer) section is a row of cooling fins. Often the thermistor looks a plastic clip attached to the fins with wires leading out the back somewhere. If the clip has fallen off, the fridge freezes. If the clip is too high, or attached to the wrong fin, the fridge freezes.
If you google 'RV thermistor' you'll find youtube vids and a replacement thermistor for under $30.