I think Dave nailed it. The Auber cannot react quickly enough to the rapid increase in heat created by the wood combustion and the insulation of the smoker prevents the temp from going down as quickly as it rose.
There are ways to avoid the combustion or at least reduce it.
1. Wrap foil around the bottom half of your wood chunks.
2. Start you smoker at 140 and run at that temperature for 45 minutes, then ramp up to your desired smoking temperature.