Sorry, but I am unclear of the question. I think it sounds as if you feel there is a temperature swing with the thermometer supplied with the grill. If I am incorrect, I apologize! I have never really trusted the supplied thermometers and I use a separate oven thermometer placed on the rack, I smoke Turkeys, fish, steaks and I find the only widely differing temperature is when the cover is removed too often. I have had the best results by planning the fire coals and soaked wood chips so that I can rely that the cover can remain undisturbed as long as possible. Sorry, If I am off-base. Good Luck.
Douglas