The temp variations you see are more from the oven temperature control then the burning of the pucks. The oven heater is only controlled by an on/off type of circuit. The set points are not very tight and couple that with the location of the temperature sensor and the load of the box acting as a giant heat sink, you end up with a variation in temperature.
At first the temperature variations were a big disappointment for me as I was expecting a very tight control with the digital. I have had mine for over a year without a problem and even though there is a variation in temperature, it has never caused a smoking failure. The hardest part for me when I first started was not understanding that if I wanted a box temperature of 210 degrees, I needed to set the temperature controller higher then 210. For hot smoking I preheat to 260 + with the box set at max 320 and the puck burner on, then load the box with the meat, add the pucks, set the timers, and fnally advance the pucks to put one on the burner. As the box temp gets up to 210, I start lowering the set point. Eventually the set point will get to the desired temperature. One thing to note is the box temp I am referring to is being measured at the location of the meat (or next to the meat on the middle rack of a multi-rack load) with a remote thermometer.
