Nunu's Q might be bugged

So i have noticed a big problem with Nunu's Q, So it is supposed to allow you to chomp on some minions/Monsters/Champions, And when you do said Chomp on the target you get health back. Well here is a problem me and my friend have noticed, And that problem is that his Q will just not go off at random time's. Now when this happens we are not silenced or anything like that, Their is no reason why Nunu's Q will not go off, In every aspect it should in the situation but it just won't. This will happen at the worse possible time's also Such as a huge team fight mid lane or just a small 2v2 bot lane. I just want to put this out as a warning and hopefully bring some attention to it because i don't want people to encounter the same problem and possibly loose a game winning fight to this bug. If Anyone has noticed this also please reply and tell me if you have had the same problem or worse.