So I grinded through the mission "play 15 games to stage 4-5" and noticed that apparently some gemes I played didn't count.
Some times when 4-5 was the stage I got K.O.ed and some times when I got way past 4-5.
I was literally at 14/15 games and I played 2 more up to 4-5 but it never updated to 15/15 games.
I thought, ok it just needs a while...since sometimes the missions take forever to update. (feels aweful btw)
So this morning I was expecting a completed mission but instead it got removed like I never did it.