Stevie doesn't like to rehearse until after 3pm.

[bombaysaffires]

I think he was mostly peeved that whoever was supposed to make sure his monitors were turned up to where he wanted them wasn't paying attention so they could have fixed them the first time he signaled that they weren't right. The more times he has to go to the side and try and get someone's attention, and the longer the problem goes unfixed, the madder he gets. And rightfully so. Like someone said, people get PAID to be on top of that stuff throughout a show. It's one thing if the sound is wonky or too low, and he signals you and you fix it. It's another thing if he's in the middle of his biggest hit at a huge festival and you aren't at your post or aren't paying attention and don't fix it so he has to go through the entire second half of the song with it all effed up. That's just falling asleep at your post.