A similar thing happened at a casino near my home in California a couple of years ago. The casino ended up giving the person the top prize of $100,000+. Legally, they are not obligated to give anyone anything at all but they did it out of goodwill. There was an obvious glitch as the machine's jackpot was less then what it said she had won. If you look closely at a slot machine you will always see words to the effect "malfunction voids all pays."