Very cool! I'm more impressed with the ingenuity of the maker community every day.
The only issue I can see (and this comes from my watching your Youtube video of the coin rejection mechanism in action) is that if you stick the wrong coin in it would be impossible to remove. It looks like it drops below the front slot far enough that it can't be reached from the front, and when the coin mechanism is inserted into the dispenser body there would be no way to reach the coin from the back as you're doing in the video. Am I seeing that right?