Blood option not spinning properly

Hi. Our centrifuge recently began not working properly when selecting the blood option. It began by accelerating then slowing this pattern would continue, now it either won't spin at all or spinning extremely slow then speeding up then slowing again. I'm thinking it's a faulty button as MCHT and urine work well. Trying to isolate the issue to see how easy it would be to repair in house or if need to just bite the bullet and send unit in for repair.