I have seen numerous posts about the Dometic ACs having this freezing problem and the usual response from the dealers is to run the fan on high instead of auto. Some have reported back that by running the fan on high they no longer experience the freezing coils.
A proper working AC should not freeze up even on low fan or auto unless something is wrong like clogged up condenser coils, or low freon, which is a problem since the unit is sealed.
I agree with you that if a new one is authorized under warranty, by all means get it and hopefully the next one will function properly.
Walter and Janie Rogers
2012 Sundance 277RL
TV 2006 Silverado 2500 6.0