@Steaming It's not a bug, it's just the rooms randomly generate each time it loads, so when your battle loads it reloads as an "empty" room which can be filled with a chest or not.
frustrating, there's no control in the game except for releasing the ball, no angle hits that change the path, you're stuck with the same route the entire game. 1/5 cause i didn't get any control over the ball's path.