Hi,
I've had a Dremel multi max tool for a few years, purchased from HomeDepot for $100. It's the kind with the vibrating head that cuts wood/metal/grout etc depending on the attachment you put on. The vibration speed is controlled by a wheel that you can select from 0 to 10 (slow-to-fast). But lately the wheel doesn't seem to work right and it speeds up and down of its own accord.

Has anyone experienced the same with theirs?
Does anyone know of a reasonable fix, or is it considered a cheap tool and time to buy a new one?

Experienced opinions and advice greatly appreciated.
Regards,
Theodore