Fridge only staying cold for 12-14 hours on AC

I have a Dometic rm2652 refrigerator in my 2011 Keystone Passport that stops cooling after 12 to 14 hours on AC power. The unit never loses power and if I swap to propane it works just fine. I have replace the heating element which was not bad in the first place and also the lower board by recommendation of my dealer. I have tested everything with a multimeter according to the manual and everything tests good. If I shut the fridgerator off and restart it on AC power it will do the same thing and cool for around 12 to 14 hours then defrost and quit Cooling. I emailed Dometic and they said the thermistor is the only other possibility which was going to be my next step. Any help would be greatly appreciated.