FWIW, I'm not an RV refrigerator expert however I do own a residential HVAC business. In modern HVAC equipment there are TONS of thermistors. Well, maybe not tons, but a whole lot of them are used. I can tell you with all but 100% certainty thermistors don't drift. They either work correctly or not at all. If they're not open or a dead short, the thermistor isn't the problem.
As far as RV refrigeration, here's the best site I've found with lots of DIY videos. Ours is in a slide as well and wasn't keeping as cold as I wanted it to. Here is the link to their video on potential issues with refrigerators in slides. I hope you find this helpful. BTW, my problem was an ID10T error as my daughter says.