Here's an answer that's in the FAQ section of some archived information.
Bradley Smoker FAQ's - Answers
Submitted by: Habanero Smoker
Q. Bisquettes do not burn completely. Is this normal?
A. After the bisquette is burnt, is should retain its shape, but noticeably be reduced in size. If you break one in half it should have a blackish color throughout. If not you may not have preheated the burner, or the burner is not getting enough power, or the burner may have a residue buildup, or your generator may not be cycling your bisquettes at regular 20 intervals, or worse – any combination of the four.
If only the first couple of bisquettes show signs of partial burning, that is a good indicator that you did not preheat the burner, or did not preheat it long enough. Turn the generator on and preheat the burn at least 20 minutes prior to loading the feeder tube. I don’t load my feeder tube until I am ready to start smoking, so I turn my generator on when I preheat the cabinet.
If you do this with the digital you will have to reset your smoke time when you load the feeder tube.
If all bisquettes consistently or intermittently show signs of partial burning; it could be caused by a dirty burner plate. You will need to clean the face of the burner plate off. The best way to clean it is to use a wire brush, and gently brush off any residue buildup. The use of denatured alcohol helps with the tough areas; just make sure your burner plate is cool. Also several have reported that this happens when they are cold smoking, so the cabinet temperature may have some control over how the bisquettes burn.
Consistent or intermittent signs of partial burning could also be a sign that the burner not getting enough voltage. Check to see if other electrical equipment is plugged into the circuit. The smoker should be plugged into its own dedicated wall circuit. If not try unplugging or not running some appliances that share the same circuit; if that is an option. If you are using an extension cord, use the shortest cord possible, and make sure it is at least a gauge 12.
If your generator is not cycling the bisquettes properly click on “My bisquettes advance, but are not cycling every 20 minutes?”.
If the problem persists contact Bradley customer service.