Well, I assume it's a bug. I think it was triggered because you pressed the keys on the keyboard too fast, so the state related to the puzzle hasn't changed to the correct one. I will upload a new version of this game if I find any solution to fix that. But right now I have no idea, I'll add a warning instead.
Thank you for playing this game, Coconut Mousse! And if you want some hints for any achievement I'm happy to help !😏