Someone has already posted about this, but in further detail I think that the moskstraumen achievement was duplicated and the id was change because the achievement did  not appear until achieved or looking on xbox.

I was hoping to get the glup glup headwear after not being sure that was the achievement that gets you that. I found out the next day that moskstraumen would get you that from my xbox beta application that crashes everytime. The achievement be read as invalid when you are looking at the glup glup headwear. Sorry if this did not seem helpful and stupid.