I don't think it ever says "audio mode" or "video mode" If it says "time base corrected" then the input buffer, which hold a second or so of audio, is engaged. This helps reduce jitter since the dac can clock out from the buffer independently of the clock on the source. The reason you can't use this feature with video is that it puts the audio out of sync with the video since the buffer introduces a delay.
So what else has changed in your system? What was the configuration like when it sounded good to you?
So what else has changed in your system? What was the configuration like when it sounded good to you?