In a quick skim of the comments so far, I don't see the real smoking gun.
The previous devices had hardware interlocks. So if the software glitched, it was just an annoying glitch - nobody got zapped. But mature software gets trusted, so they removed the hardware interlock as redundant. And then the annoying glitches became fatal. Total miscommunication. The people cost-reducing the hardware interlock only saw mature, trustworthy software. The people living with the glitches only saw them as annoying, but harmless. And then, disaster.