You might check that the wheel on the motor has not slipped. after that is it possible that the rod from the wheel on the motor connecting to the press has somehow become bent? those would be my starting place. also check the press itself to make sure that it is not binding or being blocked somehow to keep it from making a full stroke. You could eyeball the wheel to make sure that it is at tdc when the stroke is finished and at the bottom when it goes down.