Boy....never had ANY kind of problem like this in all my years of RVing. Maybe I'm lucky? Discounting my first... a popup with an ICE box.....my first TT was a used Scotty 22 footer, bought in 1985 or 1986. Dometic, electric/gas with a manual switch-over. Then a 1990 TT (Dutchman 22 footer, bought new)had a Dometic with an "auto" switch feature, and now my current motorhome, also Dometic with the automatic switch-over.
Defrost? Never any problem. Takes an afternoon. Just use what's in the fridge as much as possible, fill the ice chest with ice, put whatever is in the freezer into the ice chest...turn the fridge off...wait a couple hours (depending on the temperature, clean up any melted water in the freezer, turn it back on, give it a couple hours to start getting cold, put the food, etc.back in the freezer (and fridge)take wifeepoo out to a nice dinner, and by the time you get back...all's well.
Simply sounds like an incredible case of tinkeritis to me...but glad the OP has it under control.