Furor Teutonicus Achievment bug

I just finished the 1st Barabarossa campaign and I didn’t collect any relics and killed all other AIs, including the Cumans, I won the game, but didn’t get the achievment. Does anyone know how ? I know that 0.1% of players got it, can someone who did get it can tell me how ?

I’ve seen people with similar issues. I just got this achievement myself. Apparently, your interaction with the mercenaries you can buy for 200 gold may impact the achievement. Someone was saying if you buy them, you don’t get it and if you kill them, you don’t get it either. When I got the achievement, I ignored them all together.