check your air hose and electrical connection at the diff, a loose connection will move when you compress the suspension upon lowering it. Check to see if the lockers are locked on the ground, not hard to do, you will know it turning in tight circles.or slightly lift one tire with a floor jack (just 1") and try to rotate it in neutral, if the diif is locked, the tire on the ground will prevent rotation. If locked and the light is flashing, it is either a faulty connection or the locker switch is bad. Also make sure your diff fill plugs are not too far in, they can interfere with the locker actuator.