I am having this same problem with the refer in our 07 Classic and it is a big problem for us. On the road it does not seem to work because the temps in the unit go from 39 degrees when plugged in to shore power to as high as 60 degrees when traveling a long distance in very hot outside temps. On mild days the temp may go into the upper 40s.
I sent some e-mails to Dometic and they have sent me their part number for the air baffle. It is 3108039.003 "Air Foil Kit" for Dometic 6 and 8 cu ft models.
Also I got some advice from the Air Stream dealer to try a furnace air filter (10" by 20" I think) on the outside air vent. This seems to help but must be removed each night. So next I will try the Air Foil Kit.