Go Out With A Bang - achievement not unlocking

[Siwgrlwmp]

The achievement "Go Out With A Bang" is not unlocking. I play on Series X, but heard that it's an issue on all platforms.

I have obtained the weapon and killed 3 enemies in a single shot many times (there is a group of 3 enemies immediately after obtaining the weapon), but it never unlocks the achievement.

I tried reloading a save without perks that might have side effects, and sent my companions to the ship, and unequipped all of my other gear. This meant that my only perks were boosts to damage, so it should mean that the weapon was doing all of the damage. The achievement still wouldn't unlock.

Is this a known bug, and is there a planned fix coming soon?