I have played a few games as Twitch ADC, and noticed that popping his ult on towers works fine, however if his ult is used and you begin to attack an inhibitor, no damage is dealt. 3/3 times tried, reproduced.
Known issue - they hotfixed this in because he used to be able to damage the nexus even with nexus towers up, by shooting ult through nexus towers at the nexus. Same with inhibs.
So they made his ult unable to damage inhibs or the nexus, promised a better fix later, and never delivered because not enough people play Twitch and it's not a huge issue anyway.
