With the latest update, the achievement has been fixed and multiple players have reported making progress toward completion.
It can be only completed in Raids (PvE) and easier to farm on Easy raids.
I am going for Cargo race with as much machine guns as I can and trying to get assist or kills on all enemies.
It's a long grind of about 12-15hours I would say depending on how many you get per round played.
Congrats to Uggadunk that I believe is the first one Worldwide to get this achievement.