If this is of any help, one observation is that the glitching seems to occur (first and worst instance) at about 17 seconds. In cases where I see this with the drive status displayed, I can see the audio thread waiting (W icon) well before the 17 second mark, in very short bursts. It is only at that 17 second point (plus or minus 1 second) that there is a big audio thread starve (W icon that stays on for more than a few frames - 1/75ths of a second). This resolves, but there is a blatent audio glitch and it seems to knock the auto voladjust off (perceived sound level changes and fluctuations) for a second or so. Then it smooths out.

I will get repeated instances later in the song, but usually not as bad as that first hit.