Here's what I imagine is happening based on my limited broadcasting experience...
There are two different boards used for audio and video. They are most likely delaying the video stream to allow the board op to be able to insert the end glass advertisements when players enter the zone - the delay is so that to you viewing at home, it's not abundantly clear that the ad's are appearing and disappearing out of time. These images will be queue'd up and assigned to a button that the op has to press to insert into the broadcast when the camera is at its appropriate angle. I'm guessing the issue arises because they haven't found a perfect time to delay the audio stream. Rob Kerr, like all of us, is human and he may call the play faster at some times and slower at others.
I could be 100% wrong on this but I thought I would take my stab at an educated guess.
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