Some people report that this is bugged like the other 4 discontinued achievements, but that isn't the case. What's most likely, is people who either dont own Awakened, or are playing the base campaign, are trying to unlock this. If you try this in the main game, it will never unlock. Try loading up Awakened with a coop partner, have him shoot the wall with a rocket, and when they go down stasis them. Worked first try.