I have ran through a couple times and even did a couple checkpoints. We managed to get a platinum score but it doesn't check off for the triumph. On my first run and completion i got the Extinction Averted and plat score for each encounter but Atraks defeated didn't unlocked unfortunately.
-
I also have this bug. I have beat Atraks-1 twice now, both times with Platinum time but it still isn't checked off under the triumph "Conquer the Crypt". All of the other encounters are checked off, please help Bungie!