Temperature swings are normal per CookShack as well as other companies selling electric smokers with an analog controller. Ensure the thermometer you are using is accurate. Check it with boiling water temp for your altitude above sea level. Sometimes the thermometer is off and the smoker is fine. At other times, the opposite. If the smoker was empty, there is nothing to absorb the heat being generated. Also, for an analog controller, it is not uncommon for the initial startup to overshoot your set temp until the smoker settles down. As for calibration, I know of no way. But, you may be able to remove the knob and reposition till it matches the approximate temp you are seeing but contact the techs at CookShack before doing so if the smoker is new and under warranty.