Riven Flash-W Bug

Since the last two Patches, Riven has a bug that if you use you flash and then your W right after it, sometimes the Ki-Strike(W) won't stun. I hope this will get fixed soon because it is really frustrating, if it happens in a ranked. Here I have uploaded a Video of the Bug: https://youtu.be/FC1kiCMIcCo

I would apprechiate it if you can fix this problem RIOT.

Thank you very much!