I wonder if the knob is broken? The knobs on my old Cannon Salisbury are of very poor quality, most have been broken where the sleeve fits on to the spindle. If broken then the knob may feel as though its turning but it's just the plastic knob itself which turns without operating on the control spindle. Try pulling the knob off to check if it's still in one piece. I bought new knobs;the person who owned it before me had also bought new knobs but despite this not one them now has any markings left on the knob - very difficult with an oven knob without markings - and at least one sleeve is broken. This is dangerous because it's hard to tell if the gas is off or on!! Very poor quality!
Sue
May 2008