Ensemble cast achievement (Black Ops)?

I've tried this many times with my friends, we just now got really close. We just needed the vr11 and we got it, problem was there was no green light coming down the middle of the lighthouse. I double and triplechecked that the dials were right and I know the foghorn was right because the submarine didn't go away. I did the thing in the wheelhouse, we gave them the vodka, all the mdt thingys were destroyed. Is this just a random glitch or did I do something wrong?