Rich, have you checked the condition and operation of your fan/ventilation system on the backside of your reefer? Do you have a switch on the front or side of the cabinet to switch the vent fan ON and is it running?
Here's the installation brochure. Note that the recommended placement of the fan depends upon whether you have two metal upper/lower ventilator louvered doors...or if you have a rooftop vent. Figure 4 is what most later model Airstreams have...two metal doors, but your 27 Int's may be different...see the pdf file: (don't be mislead by conversations that argue whether the fans should "push" or "draw" the cooling air.... Dometic is clear about that matter, ...it's dependent upon the type doors and vent-exits on your trailer.):
Notice also, that there is a baffle which directs the incoming/lower air up against the back of the reefer below the condenser fins.
Hope this helps.