Problems with Dometic Duo Therm thermostat locking up

[lagreca]

I have a Dometic Duo Therm AC, with a thermostat, remote P/N: IR0101, and control board in the AC unit P/N: 3308448.004.

The problem I'm having is that the thermostat locks up periodically.
While the heat was supposed to be on in the middle of the night, just stopped cycling on. Woke up in the morning and it was cold. When I tried to adjust the temp via the IR remote, it wouldn't beep, change temp, or turn on or off. Same thing when pressing the buttons on the wall mount receiver.

The only way to get it working again is to power cycle it. Meaning I had to disconnect the AC power AND shut off the DC power, wait a few seconds, then turn it all back on, and then it works again for a while, until the problem repeats. I'm not sure if it's the receiver on the wall, or the control board inside the AC unit.

Here are Google Photos of everything: https://photos.app.goo.gl/GKukQbeFuqYt3bjVA

I bought a Honeywell Home RTH5160D1003 Non-programmable Thermostat on Amazon but as soon as I took the receiver off the wall, I realized it probably wasn't compatible, because it had a RJ11 plug.

I researched the problem a bit, and I guess these thermostats are notoriously finicky. I was wondering if it's best to repair what I currently have, or is there a way to make the Honeywell work? If I were to repair it, is it the wall mount receiver that is the problem, or the control board in the AC unit?

I hope someone in here can shed more light on my problem! Thank you.

[Flute_Man]

If I were you, I would call Dometiic and see what they say. It could be in the board, the cable and or the thermostat itself. I would start by resetting all connections on the board and the thermostat. If it happens mostly at night during the cold temperatures you might even have a cold solder joint on the board. Maybe you could find a mobile RV tech that could shed some light on that problem. Otherwise, you probably can only troubleshoot by replacement which means it could be expensive.
Personally, I would start by reseating All connections on the board and the thermostat first.