The hexagonal shaft that the rubber drive disc slides on probably needs cleaning and oiling. Do it carefully to avoid getting oil on the rubber disc.

Stand the unit up on its nose and safely secure it in that position. Remove the plate on the underside of the unit and you'll see the horizontal hexagonal shaft. It will probably be a dry-looking black. I use grease for lubrication. Slide the disc a few times to distribute the grease.

I get these in the shop all the time. Like the posters said, that bar needs to be lubricated. I like to use Some liquid wrench and a paper shop towel. I wipe the bar down and then apply the grease and yes, be very careful not to get grease on the wheel or the smooth friction plate. If you do get some on either of those, clean them real well and you will be all set. Patrick