Mr. Mix curse should not be broken, just trigger the minigame at the menu, get a time's up gameover, try to press esc key to quit, it won't let you, but you now have the achievement even when the achievement get text doesn't appear, so close the entire game manually with task manager, restart the game, go to your achievement board and it should be there. If this doesn't work, it may be broken, because I already have it.
Viewing post in Advanced Education with Viktor Strobovski comments
It worked! Oh my god, this is so cool! But sadly, the „curse“ just happens once. I mean the creepy noises. I wanted to record it, while this happens, I even reset my achievments, because I thought, it might happen again, if I do that, but no. Instead, I just recorded the mini game, but without the curse. Thank you for telling me how it‘s done!