try wind it up a bit then down a bit to try lossen it until it moves up then go over all the threads with a wire brush really scrub them till there clean then smear some copper grease or Vaseline if ya haven't the copper grease try then to lower the ring even get a piece of timber to tap the adjuster ring in one of the grooves the timber will give before the ring does better than bashing it with a flat head screw driver