I recently purchased a multi format disc player and half a dozen SACD/DVD-A titles to enjoy. One of the discs has started pulsing during playback. Not sure if that's the correct term, but it sounds like someone is constantly moving the volume up and down, up and down, or more accurately, adjusting a tone control up and down. None of the other discs exhibit this behavior and I could swear that the first few times I listened to this disc the problem was not present. Any ideas?