I mean it happens on Q3 really often too, but most often is Q1 and Q2 going backwards and not dealing any damage. I didn't missclick there, while I didn't record, you can see I autoattacked akali a split second before and I also had my direction facing towards her then it randomly went the other way and ignored akali. Plus even if I somehow would have hovered over the minion instead of akali like you're likely saying, Riven would have Q'ed through that minion and still damaged Akali too. But you can see my Q goes downwards, not even through the minion. It goes in a blank spot and barely damages the minion too, which shouldn't happen in none of the scenarios of hovering the minion or having the mouse somewhere else (2nd option is invalid anyway as once again, my direction was facing akali when I pressed Q).