I've got an idea but it's long and complicated.
Some Dometics, and I think the RM2652 is among them, have a Low Ambient Temperature switch located on the inside upper door frame. You have to open the door to see it. and it might be labeled just "LAT". Turning it on will keep the light on inside the refrigerator and will add enough heat to keep from freezing inside.
It's purpose isn't to keep the box from freezing, however. There's a thermistor is located in the box and when it's cold outside, it doesn't call for "cool" and the refrigerator won't kick on. The box is happy but the ice cream in the freezer melts.
So turning on the switch might temporarily cure the problem in cold weather but it sounds like the thermistor isn't working properly. It's supposed to shut down the cooling action before the beer freezes in the box. You can adjust the inside temp up somewhat by moving the thermistor down on the fins at the back of the box. Of course, if it's fallen off the fins and dangling in space, then that's the problem. It has be attached to a fin. Your owner's manual should tell you which one, probably the second from right, about 2/3 of the way up.
If it's in place and the box is freezing up, the thermistor needs to be tested. You don't have to take it out, just remove the harness for it from the board and check the resistance (ohms). It doesn't "click-on" like most sensors, it varies according to the temperature on the probe end. Here's a chart:
20 deg.=13376 ohm
30 deg.=9932 ohm
32 deg.=9370 ohm
36 deg.=8847 ohm
40 deg.=7448 ohm
45 deg.=6473 ohm
55 deg.=4925 ohm
70 deg.=3325 ohm
If the thermistor is in place and tests OK, then the board is likely bad and needs tested. This, however, takes a board tester.
If you do turn on the LAT switch, be sure to remember to turn if off before summer or the refrigerator will run constantly and won't be able to keep up.