[taneq]

From a functional safety perspective if you can't verify each step from the initial risk assessment to the final product, you can't prove the overall risk reduction and therefore don't know the overall residual hazard. From that perspective this sub would never have left dry dock (or possibly the CAD model).

In practical terms if push came to shove, an Xbox or PS controller is probably more reliable than most equivalent devices. My stock phrase when comparing normal functions with Safety Instrumented Functions is "I'd trust this with my car, but not my life."