Help, 2003 Arctic Fox fridge isn’t staying cool when on DC

for about $500 you can upgrade the Cooling unit to one of the Amish Built ones. My old cooling unit failed and I installed a new Amish one about 2 weeks ago. So far the performance of the new unit is substantially better on AC, DC and Propane. At 100F outside the Fridge stayed at 35 and the Freezer kept the Ice Cream frozen solid. I had it on DC while driving and Propane while dry camping

https://rvcoolingunit.com/Norcold-Cooling-Units-remanufactured-C4434.aspx