We have heard about goals against one player's own team in football, but it also happened in the boxing arena: H. Wallitsch was fighting Bartolo Soni in Long Island, USA, the night of December 12, 1959. The fight was fair and even until Wallitsch tried to hit hard his opponent.
As a product of that attempt, he lost his balance and went against the ropes; after being entangled, he fell out of the ring and hit with his head first into the ground and producing his own K.O.
That night, surely enough many gamblers wanted to cut their own veins. There is no form of advice, tip or hint that could save a bet from falling thorough due to such things.