Thieving is a crime, no matter who the victim is. Despite the fact that it is another "big business" that can "afford" to be ripped off, it is still beholden to it's shareholders, employees, and present and future customers.
I see your point and a truly moral person should immediately tell the casino that their one-armed bandit machine was going crazy. But was it theft on the part of the players who were just using the casino's machine?