This has happened twice to me. First time I killed two hunters and only received commendation credit for one. I saw the medal in game for both and my post match stats registered with two boss kills. Second time I killed warden eternal. Everything seemed to be in order, got the medal in game, my team got the points, notification in the bottom left kill feed. However when I looked at my post game commendations my kill was not registered. Mildly annoying, last on the to-do list of things to fix.