Sorry about that, it's probably because you restarted from a checkpoint 😬 As it stands now, you can only get all painted tiles by not restarting from a checkpoint at all, so doing it in one go.
Thank you for the feedback! I do want to polish it, the puzzle mechanic didn't really work while playtesting & designing levels. But I had to wrap it up and get it released despite that. Maybe I can improve the idea behind it to make more interesting puzzles than what it has now.