Warwick's W improperly displaying

Frequently, Warwick's W - Hunter's Call - will display as available for casting instead of on cooldown. I am unsure if it just is not functioning properly or if it is just improperly displaying as available for cast when it is, in actuality, on cooldown. So basically, you think you have W to cast, you mash on it a bunch, and it doesn't work. This happens quite frequently, several times a game whenever I play him.