I've had a 7 lb brisket in my Masterbuilt electric smoker for almost 3 hours at 220 degrees and it is already at 156 degrees. Isn't this way too fast? I thought it would have to cook for hours yet. I'm not a very experienced smoker. It looks fine but not nearly cooked by appearance. I checked my thermometer. :( Can anybody help? $35 brisket!