I remember reading a story like this from the early days of Acorn. The first production sample of the BBC Micro came in, and would crash unexpectedly. Trial and error found that connecting a jumper wire between 2 particular points on the board stopped it crashing, but nobody could work out why it crashed or how that fixed it. They never worked it out and ended up shipping mass quantities of the BBC Micro with the magic jumper wire in place on each one.