The "Flight Lessons: Air Combat" portion of the "Nevermore IV: The Raven Spirit" Achievement

The eponymous part of the achievement has a glitchy trigger and seems to either have no chance or an extremely low chance of triggering when Mouth of Mordremoth is 1-burned. I tried to complete it several times with the Raven chick in my inventory with no luck, only managing to get it when I joined a Dragon's Stand map with less people in it so Mordremoth wasn't beaten in one go.

If this is something devs can do, an easy solution may be to create a second trigger for the achievement tied to looting the boss chest so if beating the boss too quickly glitches out the first trigger looting the boss chest triggers the achievement for the player instead. Since you have to have fought the boss to loot the chest, the fact you're looting it should be proof enough you met the criteria.