As mentioned here,
Vi's Q has a current bug. Occasionaly when you press Q, it will "charge" up while not showing the aimer for it, and you are forced to stand there doing nothing until it runs out. This has killed me many times, and has been there since her release and has seem to have gotten no attention, dispite seeing other forum posts on it.
Posted to Help & Support aswell, unsure where to post.
Any feedback/help i will be more likely to check the reddit,
Take Care! ~Crave