Even with an individual error, the system/office/company put the individual in the position to make the mistake, and then didn't provide adequate accommodation or procedure to prevent the mistake.

Not every individual mistake can reasonably be averted with changes to the system, but it's vitally important that we at least ask the question of how the system failed. Otherwise we're virtually guaranteed to wind up with a pile of "unrelated incidents" that might have been prevented at little to no cost.