Refuse Correct Change

Not only is Robby not accepting $1 bills, but he is not taking nickels, dimes, or quarters. All of these coins get stuck almost immediately upon insertion. If you subsequently jab Robby in the right place, they fall to the coin return. This happens to also be, thankfully, and somewhat surprisingly, the end result when you hit his coin return button.

Unfortunately I didn't have my $0.90 coin on me to purchase the bag of pretzels which was screaming "Eat me!!!"