Temp problems on smoker

I currently have a 7' three door offset smoker with tru-tel gauges on each door and three rack thermometer inside. When cooking my tru-tel gauges always show temp 50 to 75 degrees cooler than the rack thermometers. I thought the problem may be the stems on the tru-tel are only 3” long and only extend past the inside of smoker lid by a ¼”.


Does anyone know how far the stem should extend into the cooker? Any help would be greatly appreciated.