Im not familiar with the tailgate but I assume it is small. With you being in AZ I assume the ambient temps and small grill might be your problem. If it is close to 100 degrees outside the ambient temp in a grill could already be over 100 degrees. Now trying to keep a fire built in a grill that small and keep the temps low is hard to do. I bet if you were in cold temps, it would do better at holding a lower temp. Also are you relying on a Traeger probe for your temp or do you have an aftermarket one? I wouldn't trust a the Traeger sensors, they are notoriously inaccurate.
