tension got nothing to do with needle shaft movement.if you mean tension the small wheel on side of hand wheel,that make sense.remove small wheel by removing small screw and ensure star shape washer is placed with higher part against small wheel.clean and refit,refit screw.if you find that small wheel does not release handwheel if small wheel is turned anticlock remove screw turn starshape one notch and try again.depending on when last machine was serviced it could also mean seized main shaft cause of to little oil
johan
January 2012