Poro King, delay on Alistars Pulverize?

It seems to be that randomly I can't use Pulverize (Q) after I land a poro toss. It can take up to 1½-2 seconds before I can get it off, despite spamming it from the moment I land. It's off cooldown and no CC involved. Sometimes though it works as it should and goes off instantly. It's really inconsistent and creates some really bad gameplay moments. I'm not sure what could be causing it.

I've only been playing Alistar on the game mode, and experienced it every single match so far. I don't know if it happens with other champions as well.