If I had to hazard a guess, my (admittedly, poor-educated) opinion is that the issue has to do with the fancy new environmental audio program that you can buy. Since the issue seems to be oriented around positional audio cues (there's a couple of threads about that where moving the camera in certain ways, or changing the audio position from camera to character changes the problems - at least in 6.0), my guess is that something with the audio encoding for the fancy new environmental program is the problem.