[DaiPlusPlus]

My understanding is that it was a UX issue - the "malfunctioning" was the system working as-directed by the user, but the UX was horrible for informing the user what they were doing.

[gonehome]

It was a lot worse than that: http://sunnyday.mit.edu/papers/therac.pdf

That paper is long, but does a great job of giving the context and going deep on the details.

[DaiPlusPlus]

Thank you!