Just received this brand new Festina watch and knew that the battery would need replacing. It has sat in a drawer for a few years and never had a battery replacement. I managed to get one screw out but the other three I can't get to budge. I'm frightened to use too much force because I don't want to damage the screw slot or snap the head off the screw. I'm not a big fan of this caseback arrangement, but there's probably not much choice with the case shape. Any tips to loosen the screws?