Ornn bug?

Before we start I know I play Ornn a tonne and he's busted cause tanks and all with their % max hp damage but recently I've been noticing that whenever I use W - Bellow's Breath and I make a champ Brittle, whenever I walk up to 'clap' them, occasionally Ornn will just sit there and he won't auto attack let alone even start the animation. It's obsurd how many times he it has lost me a trade and/or gotten me killed it's insane and I hate it.

Also, it doesn't feel like an aa cancel because it works fine most of the time but then every now and again this pops up??!! And if it was an aa cancel then why does he not even start the animation?