My personal favorite is when everyone knows music is playing but can't hear it enough to get in clapping rhythm, then there's that awkward 3-4 second transition while everyone tries to get in sync with the music after it quiets down a bit.
This has been bothering me all year. It takes a lot away from how crazy it could get in there. It sounds like a technical problem rather than by choice because when the volume goes up a little the sound starts to distort. I hope it gets fixed some time this year, hopefully by Monday.