Hi
I have this model of cooker too and I have noticed the same thing happening. I found that if I make sure the off switch is actually off and you can't see any red/orange then it is truly off. I have had my cooker for twenty years and have had no trouble with it. Sometimes the oven knob sticks and I can't turn that off. I turn it off as much as poss and then when it cools down slightly it turns off. I suppose it's wear and tear of the knobs. Hope this helps.
Cheryl Colley, February 2009