Cho'Gath Ultimate Bug.
Edit: When watching it on .25 speed I noticed Vel'Koz's Passive proc at the same time, so I think that might have something to do with it.
When slowed down it shows that the ultimate is consumed and put on cooldown. From my perspective when playing it was consumed. From my teammates perspective it was not.
When played normal speed the ultimate is consumed and not put on cooldown. That is what my teammates saw and pinged that is was ready. Even when it was on cooldown for me. I do not know if I was still able to use it. I didn't think to try.
For the video of the pings I slowed down the replay of nautilus' death, so it would show the cooldown. My teams pings showed that it said it was ready. Even though it was on cooldown for me.
When I went to use my ultimate i am pretty sure I used it at the same time nautilus died, so it went on cooldown. To my team it said that my ultimate was ready. While for me it was on cooldown. In the replay is slowed I slowed it down (to .25 speed) and after using the ult it goes on cooldown. It even shows that i used the mana for the ult. Even though no damage was dealt because he was already dead. When played on normal speed it shows that my ultimate is ready to be used.