At first, it looked like just another glitch. Then all of a sudden an outage wiped out power in the Midwestern United States and Ontario for 7 hours.
In 2003, a minor software error in a control room alarm system led to a situation where operators remained unaware of overloaded transmission lines.
That small software glitch led to the collapse of the whole electric grid. The disaster led to significant economical issues, and to an estimated 100 deaths.
If you study big software originated incidents closely enough, it turns out that the problems aren’t caused by those big and hairy showstopper bugs. Usually it’s the small errors that are so easy to ignore.
Don’t fall into the trap of evaluating bugs by their appearance; Evaluate their impact instead!