Kindred Ult Bug

In about 70% of the kindred games i play, partway through the game (around 15 minutes in) i lose the ability to ult. From that point on, my ult is always on cooldown and can never be used. It first happened to me right after kindred first came out, and i figured it would be fixed by now. it hasn't. please help, rito! Kindred almost isnt worth playing if she doesn't ahve an ulti at all!