The control box azimuth indicator is not tracking smoothly with the drive unit. It will swing normally through an arc of about 90 degrees but then starts traveling in 1 degree jerks so the display cannot show me the true compass rose direction. The box will still rotate the drive unit through 450 degrees. I looked at the gears in operation and couldn't see any misalignment. My thought is that a fiber or hair. may be causing this. The belt does not seem to be slipping. Perhaps replacing the box motor and belt will fix this. I have lubricated the gears with copious amounts of silicone spray and blown it out with compressed air but no joy. Suggestions???