Hi, I have an AEG HC 5690 3360 cooker hood. There is an intertermittent problem whereby the fan-speed selection switches will not latch. I suspect over the years (6) they have become a bit greased up and plan to replace them if I could find a way to get them out of the cooker hood. I can get to the rear of them via the filter removal, but don't want to force anything. Any suggestions would be appreciated.