Story progress is shown at 60% even at the end of the game.

Sometimes, tumblestones will get "stuck" a column below where they should be. Selecting it makes them fall back to where they are supposed to be. I forget exactly which modifier causes this.

Very minor: After the credits roll, it will return to the map screen of the final world. The rock king will then stomp whichever level is below it. This won't necessarily be the last level. Reloading makes the crumbled level sign return to normal.

Finally, not a bug but a feature request: Why do none of the arcade modes allow for modifier? Infinipuzzle does, but it only allows for one modifier at a time.