This reminds me of (I think) Richard Feynman's comment about the Challenger, to the effect that when the o-rings were eroded by 1/3 or whatever, they called that a safety factor of 3, whereas they should have stopped and said "wait, it wasn't supposed to do that at all, something is seriously wrong".

I'm not sure if it was him or someone else that pointed out when you do a post-mortem on a disaster, you generally find a history of near-misses, but people don't take near-misses as seriously as they should.