Redundancy also adds a lot of complexity, as fail-over mechanisms aren't simple either. That added complexity then turns into additional possible error sources.
A friend of mine builds a component for a satellite system and the FDIR mechanisms need to be chosen very carefully, as adding more fail-safes can actually make the system overall more error prone.
There's an interesting blog post on from AWS about that topic [0]. Turns out adding more fallbacks and fail-safes is actually discouraged there.
