Okay so I have already finished all the cases and got all the badges once. Last night I finished the first case for the 2nd time but its not showing the 2x beside the badge. After finishing the case I stayed on and played a few more puzzles of the next case and it showed that I completed the first case but I don't have the 2x. Ohh and after completing a case I always clear stats because if I don't the game will mess up and freeze and lose progress for me, but I didn't do that this last time.
maybe since you cleared stats the first time, they think you've only done it once according to the stats so they dont credit you with x2.