This is a common issue and can be resolved. It requires some disassembly of the burner and chute and some modifications.
The puck shown in your photo appears to have found its way completely onto the burner but you will find that some do and some don't. It is the contact between the puck on the burner and the one waiting in line that causes the trailing puck to ignite too soon. It will smolder on the chute waiting its turn and deposits the soot and ash on to the chute making it rough and not ideal for the pucks to slide along during the smoke process. The build up of residue just gets worse and worse as each puck burns before reaching the burner. Some times the leading puck will straddle the burner plate and chute by about 1/4 inch and sit on an angle leading to uneven burning and still causing pre-ignition of the trailing puck.
Here is a link to a thread that details this issue and how to fix it. I made the changes and it improved puck burning on the burner and minimized the pre ignition of the trailing puck. I rarely have to clean the chute as the pucks are not burning on it anymore. Pucks burn far more efficiently now.
http://forum.bradleysmoker.com/index.php?topic=36796.0