My Air units turn themselves off

[Downsizing]

I have a keystone alpine 5th wheel. Bought in 8/2020. The air has never worked right. The Gateways were replaced and the entire In-Command system was replaced, but still the units turn off either after reaching temp or before and won’t come back on unless I turn them off at the InCommand control board and back on after a few seconds. Seems to reset and start up again. Been 6 times to repair and no one can figure out the problem. They insist it’s not with the units themselves, but what else is left?  They work fine if it’s not too hot outside. And the heater on one unit works fine too.