In 1997, Garry Kasparov and IBM’s Deep Blue competed in a chess match, where Deep Blue won the match. This was a rematch from 1996, Kasparov won the first match, and IBM went off to improve the chess-playing ability of Deep Blue.
In the first game of the 1997 match, on move 44, Deep Blue made a counter-intuitive move, which Kasparov didn’t understand. He thought the machine had finally developed superior intelligence and would out-play him. Afterwards, the IBM team concluded that move was really a bug in the program.
Big Blue went on to win the match, perhaps because Kasparov’s confidence was shaken by the buggy software?