Autofill when it shouldn't
Today i launched a game with a friend. I tagged top/mid and him bottom/top. I got autofilled (no problem with that) in bottom. And my friend top.
I would have more sense to put my friend in bot and me in top.
I imagine that it's pretty difficult to correct in the matchmaking algorithm but adding a correction part after the choice of player would enhance it. (And mostly correct visible error so have a big positive impact on the player vision of the matchmaking).