The icing over is quite easy to see from the bottom side with air filter cover dropped down... This happens to us sometimes when it is a real humid night...
For us however we usually just shut down the unit and it is good to go again in 15-30 minutes later.
This could also be a LOW VOLTAGE coming from the camp ground pedestal... I have one of these RV120VAC PLUG in AC VOLTMETER units that I can glance at. I like it because it has the "SAFE ZONE" green scale marked on the front. If the AC VOLTAGE is outside the green scale we will not turn on our air conditioner.
Roy Ken