Molten Lava
Smash Cadet
In 2.6b, when I attempted to change the music in Metal Cavern, the game would freeze if I went any further down in the list then what shows up automatically (the first 4 songs). I figured this was an issue with my specific download, so I didn't report it, but the same bug is in 3.0. This is probably an issue with the stage Metal Cavern is over, so fixing it might not be possible, but I still feel like it's worth reporting.