> Is it fair to expect a random engineer who was ordered by his company to rewrite the code to work without a hardware interlock to know what he doesn't know? No.

Looking back at when I did Safety Critical Systems at Uni way back in another era, the most important points that we got out of the Therac-25 case study were not to do with bugs at all, but to do with the deficiencies of the system architecture and methodology, especially the decisions that led up to it.