I've noticed a similar problem with specific cdlc's. In my case the guitar sound is dropped to zero so I cannot hear my bass at all but the game still registers the notes I play so I can get a score. After this happens, the sound on the guitar never returns until I exit and reload the game. It's very noticeable for me because I get the player volume 20% higher than the music. It appears like something in the cdlc is lowering my volume setting but I can't find in the files extracted where this might be set.
