I have a 5 year old Servis quartz M9130 which has stopped turning at all with a full load, and which turns in only one direction when there's anything more than a very light load in. I've had the back off, and there's nothing wrong with the belt. With a light load, the motor's turning the drum clockwise, but can't manage it anticlockwise and just 'strains' instead. Is this just an old, tired motor, or should I be cleaning certain bits of it to help it along?