I went into a fireteam of 5 to do the bells sequence. First time we got it the sound went off and wolves howled and all but one of us got it. I promoted him to leader and we went to orbit then down again got it timed perfectly again so the noise went and the howls stuck but he still did not get the achievement. He has tried signing out and resetting his xbox to no effect. Hopefully this is an isolated incident but i doubt it. He was on bell 2 the whole time if that matters.