legality of a vending machine eating your money?

What is the legality of a vending machine eating your money?

Let say you put in a $5, it gives you no change and no product.

Could the owner/operator simple say that you agreed to give it money willfully but they are under no obligation for the quality of the product/service( in this case being nothing given). Something like that or is this some form of thief/fraud?

Thanks.