I hope someone can help! I have a Hygena / diplomat oven (AHY 3300 – Select 610) and the temperature / on / off / grill knob has just fallen off! When I put it back on again, it doesn’t switch on in the position it should do, and doesn’t switch on and off in the same position every time. I also can’t get the grill to work. Any ideas? Do I need to get a new knob or an engineer in to look at it?