Side note: I really dislike a particular vending machine at my work. Put the money in. Made a selection. The chips started moving but they got stuck at the very end. Can't a girl just get some dang chips?
It may be to late to reply, but have you tried kicking it? You've paid for your chips, so you should be able to get them by fair means or foul.
I know that kicking a vending machine is disallowed in most places, but sometimes the end justifies the means.