Thank you so much for your feedback! :). If you'd still like to finish the game: we updated the game to fix a few game breaking bugs and uploaded a walkthough.
After taking a look at the walkthrough, I was now able to finish the game. I still noticed a few small cosmetic bugs: The "real" head remains on the shelf as a duplicate and its owner loses his recovered head from time to time (when turning around?). However, the game can now be finished without any problems.
Looks good, sounds good and has a really clever game mechanic. Great game! Highly enjoyable. :)