I didn’t notice this until the Soundcloud was put up for the soundtrack, but after going there I had to go back in-game to double-check and find that the bug does indeed exist.
The mine cart destruction bonus stage doesn’t have the Bonus Stage soundtrack playing! Instead, the Rapids theme from World 2 plays in the background.
Clearly we need a hotfix to make the proper theme play for this very important segment of the Super Adventure Box.
Josh?