Nunu "Absolute Zero" bug

There is a bug I've been experiencing with where when you press R (or whatever keybinding you have your ult set to) it casts the ult, but makes it to where you cant cancel the channel early like you should and you have to be forced to stand still for 3 seconds and cast an ult that nobody is even in and immediately puts it on cooldown. It just lost me a game where I could've easily won a teamfight but the ult bugged and caused us to lose a teamfight that led into a baron push.