Riven Q bug

This bug is quite happens with extremely high frequency (I probably encounter it at least 1/2 riven games). I don't know what causes it, something to do with Riven's fast Q combo, but she will sometimes just Q in place instead of dashing towards her target. You can tell it's a bug because if I missed his model when I Q'd then Riven would have dashed forwards, but in this case she just spins around in place. I've lost many kills because of this.