Friend and I were penalized for autofill teammate

The system gave my friend and I a penalty. Neither of us were cheating and the system even named the offender "nyatko." We maybe had two games max with the cheater and didn't know he was even cheating until we got the penalty. After that, we played games without the cheater and everything went ok; we had a couple successful raids and a couple fails.

It said we obtained koen abnormally and we should alter our behavior and not play with cheaters. How are we supposed to know who's cheating? Should we only play as two without auto fill at a disadvantage to us with potential four stacks in the lobby? How is this fair?

Crazy that an in game feature created by the developers is directly the cause of us being penalized.