Katarina's ultimate

Hello, Katarina is one of my favorite champions, I've played her for years and I know her mechanics very well (Yeah I know she's not hard to play and bla bla) but my point is.. I am pretty used to play her, and there is a thing i've been noticing since the last few patches, her R doesn't always work in certain situations, after a quick shunpo or any other spell, it doesn't feel smooth anymore, I've played her for years like I said, and only lately it happens to me that her ultimate WON'T work if you use it fast after another spell, I have to press R twice. So I am either developing arthritis, or there is a small bug with her ultimate not working instanlty after a spell like it used to. I'd really appreciate if this was checked by riot, and it'd be useful to know if any of you have felt this lately too.