Reproducing the problem not only allows in depth debugging but the conditions needed to reproduce can give clues as to the cause. The most significant/interesti

Reproducing the problem not only allows in depth debugging but the conditions needed to reproduce can give clues as to the cause. The most significant/interesting bug of my career was a problem in 1978 with a Linotron 606 phototypesetter at the Auckland Star newspaper in NZ that occasionally would have a small patch of mangled text at a random place in the job. Reprint the text again and the problem would disappear. The problem had been outstanding for several months as it wasn't a showstopper. The hardware engineer and I figured it might be related to how the fonts were pulled off disk and put in the typesetting memory buffer so we set up some artificial disk transfer errors where every 50th transfer would fail and sure enough this made the problem happen 100% of the time. From there simply inspecting the code that transferred the fonts we found the problem which was that an extra blank character used for filling the background in reverse video (white text on black background) which was put at the top of the buffer was omitted when things were redone after a disk transfer error. So all the character addresses in the buffer were incorrect resulting in mangled characters.