It could be scoring on the spindle, corrosion, dirt, there are loads of different reasons. Slacken the variator nut off (don't take it off completely), take the belt off and give it a good spray with some WD-40. Then lightly tap the variator pulley with a hammer, using a block of wood to prevent damaging it to see if you can shock it free. You do need to take it off to see what condition the spindle is in.
