@venomandri
I think I know what this "bug" is.
It's the: "dynamic background music" feature but you can't turn it off. (I searched the whole settings multiple times) so is there a way to turn this feature off?
(Yes, if you make a mod which is using this feature everything is fine but for me personally i'd like to turn this feature off) (Sorry for my bad english... i'm not a native english speaker)

@cadamon
I have the same problem as you do but I also have a bug besides this.
If i download a mod which has multiple background songs it plays one of them but every time I left and right click on my mouse the other songs from that same mod start to fade in a little bit and then fade out again.

I don’t know how, I don’t know why and I need some help because I can’t surf without some music.

Thanks