This didn't produce an error or anything so I can't share, but what I have been experiencing is the in-game music (as in the default music) starts playing, but then other in-game tracks starts playing over the initial track. Doesn't happen in vanilla, but with Forge it starts becoming a problem as one track doesn't naturally flow to the next as one track plays over the other before the first ends.
Looked in the forum and couldn't find if it's been mentioned, and it's nowhere to be found.
I'm sorry but this is all the info I can put up.