It’s complicated
Employee is liable for not telling boss he can't guarantee behavior doing this. N-1 layers of management inaccurately assessed and mismanaged the reasonably foreseeable risk. Literally the only one not culpable in the entire chain is the machine itself.
Appeals to "It's complicated" constitute the crumple zone desired by people who really need the aforestated to not be the case to keep being paid.
As it turns out, if you hold people to an standard of reasonable forseeability, and don't let them set the goalposts at 2nd degree arbitrarily, there isn't much you can actually get away with. The steps aren't hard to manage when you actually take the time to think about them.