I have seen the vid and can't quite work out the cause of the noise you have - it will either be the gearing or the motor - disassembly and inspection may be your best way forward. Years ago my mother's machine broke down - a nylon gear set had lost a couple of teeth - kenwood kindly sent replacements "cash on delivery" - so trusting of them. Excellent customer service.
Over time powder from icing sugar and flour gets inside - it may benefit from a good internal clean up.
Good luck...
Peccavi
October 2009