I can't get the realistic achievement for R6V2

I tried everything.
first I ended the game as knight over xbox live, no achievement.
Then, as bishop over xbox live, no achievement even though every player i was playing with got it.
I played scenes as knight, no achievement. So please people, if it worked for you it is not the solution.
I played the first and last scenes as knight and bishop, no achievement.
I played single player as bishop from beginning to end and no achievement.
I played a random scene knight over live and no achievement.
I did all the scenarios posted on these forums and no achievement.

I if you know a solution other then these, post please. otherwise, I don't want to here I got it with no problem because that doesn't help anyone. Thanks in advance.

I got it no problem...

Just kidding, I'll never earn that achievement I'm pretty lousy at the game...

I heard about many others with the same problem... devs said they were aware and preparing a patch to remedy the issue (along with the private first class, which was also a problem)

i've never seen a glitch like this. Now glitches involve achievements? What's next?