Q sometimes does not work

I have encountered a bug where I cant cast q. doesn't happen that often but when it does it last for maybe 1-2 sec, its not that noticeable on champions that don't spam q that much but when you play Kha'zix, Rengar and Hecarim it gets pretty annoying ,i have changed keyboard and even tried it on other pcs, and have asked some friends if they have the same issues and most of them have answered with yes. I feel like I encountered it most in team fights when I am using my q a lot (but never happens when I clearing camps tho, it only happens when trying to use q on champions) I don't think me being from Serbia has anything to do with it and my internet connection is good. [zombie-nunu-bummed]