I notice that when the episodes start or a chapter break, the audio takes a couple of seconds to come up, and it fades in. But if I skip back to the start, it's fine. But I really don't want to have to do that...
I'm having a similar problem with the season 2 discs on my Panasonic BD30 player. I haven't tried the mono tracks, just the stereo tracks, and it happens only at the beginning of an episode. I have all firmware updates installed on the player.