Turntable drive is loose
Turntable drive spindle appears loose so it surges ahead and then stops and starts again irregularly over and over. Can I remove the bottom of the case to inspect it?
Are you sure it is the turntable drive motor spindle being loose and not the turntable roller ring?
Check all three rollers and see if there are flat spots. These flat areas on the rollers prevent the turntable from rotating smoothly. If the roller is ""sitting"" on the flat spot the turntable might not even initially start to turn. When it does it might jerk and stutter, especially if there are flat spots on the other wheels as well.
If there are flat spots, unfortunateley you cannot buy just the rollers, you have to buy the whole ring."