Even with more robust hardware (and the question says that their hardware is designed for this environment), software redundancy and error checking can still be

Even with more robust hardware (and the question says that their hardware is designed for this environment), software redundancy and error checking can still be worthwhile, even when it only means that you catch the hardware malfunctioning rather than being able to fix the error. Still, for things that are really mission-critical, I'm not sure there's any substitute for full-blown hardware redundancy, e.g. having 3 computers and requiring 2 of them to agree on an action (via an interlock mechanism that is itself robust and redundant, which is a whole other can of worms...).