Mipper, Bradley bisquettes aren’t intended to burn to ash. They just char through, leaving a charred black puck.
Under some circumstances bisquettes may not char completely. The situations that I know of that result in incomplete char include bisquettes that have absorbed moisture from the air, quite cold weather, certain types of wood tend to have incomplete char more often (oak is one, if I remember correctly), or due to puck density variation from puck to puck.
I don’t worry about the instances of incomplete char that I experience. It doesn’t seem to affect the quality of what I am smoking.