diana q bug

IT has happened to me on a couple oocasions where dianas q does not explode at the end of its animation causing enemies which would normaly have been hit to not be hit. IT would not be so devistating if her ult did not rely on moonlight. I just played a game where a vayne used her tumble as i used my e. I then used cresent strike to hit her but it went completely through her doing no damage. I then ulted her because i thought i hit her but my ult went on cooldown and i was completely screwed. This has happened to me on mulitple occasions where my q just goes right through the enemy.