The position of the Temp Thermister really has no bearing on your type problem. They should have hot wired the 2 120 elements for 24 hours/blocked off the drain tube for the evap pan tray and run it. After obviously checking the door seals. Now, IF the outer silver box insulation has deteriorated over the years, it has lost the insulation capacity and the complete refer must be replaced. You must pull the refer to examine the sides of the insulated box and if it had looseness and voids behind the silver cardboard, the box is ruined. I had this happen last year to a customers 12 year old 1200 and after contacting Norcold, they informed of this problem they became aware of about 2 years ago on older 1200 models that experianced your type problem. Like I said, lack of cooling from thermal mastic incorrectly installed is only noticed while in transit. It IS possible, the CU was not charged correctly by the rebuilder. Doug