[JRTJH]

What hasn't yet been addressed is the question, "Why is it OK for the refrigerator to operate when towing and it's not level when on the road?"

The answer is contained in both the Dometic and the NorCold owner's manuals. The "rocking of the RV when in motion prevents pooling of the coolant and damage to the system from that pooling"

Many (probably most) RV'ers tow with their refrigerators operating without any problems. When parked "off level" for a length of time (hour or more) the ammonia/hydrogen/sulfur coolant can pool in low spots and the sulfur will settle out and solidify, causing a blockage of the coolant pathway. When towing, the RV rocks and bounces down the roadway, because of this motion, there is no risk of the coolant pooling in low spots as the motion keeps it from becoming stagnant.

Hope this helps.