It's very hard to ensure you capture every single possible failure mode. Yes, the engineering control is important but it's not the most critical. What to do if

It's very hard to ensure you capture every single possible failure mode. Yes, the engineering control is important but it's not the most critical. What to do if it does fail (for any reason) is the truly critical control, because it solves for the possibility of not knowing every possible way something might fail and therefore missing some way to prevent a failure