Ultimate Sometimes Doesn't Work as Nautilus

On ocassions when I try to ult someone as Nautilus nothing happens. Like I click R, then I click the person who is in my range and absolutely nothing happens other than the indicator goes away. It is not very common for this to occur but it has happened in a couple of different games now. Unfortunately, I'm not sure what causes it. When it happens, it usually is stuck like that until I die and then when I respawn my ult works like normal again. Hope this gets fixed soon, since when this does happen it often becomes a huge detriment thinking I have ult since it is off cooldown but then it just doesn't work. Not sure if this happens on other champions either, I've only noticed it happening when I play Nautilus.