A negative outcome is a system failure, even if it is a personal failure that drove the outcome, because that is a failure of the system to prevent personal failures from causing negative outcomes.
You can't stop personal failures from happening because people are people. You can design processes to minimize or eliminate those personal failures from yielding negative outcomes.
But too much system can also cause negative outcomes, because all that system has a cost, both in money and in time. If you add a protection to prevent every negative outcome, your system will never produce anything at all, which is a negative outcome.
Every check has a cost. For some checks, the cost is more than it prevents. Don't add those checks, even after the negative outcome happens.
You can't stop personal failures from happening because people are people. You can design processes to minimize or eliminate those personal failures from yielding negative outcomes.