At the beginning of space flight in USA the purported philosophy was Zero Errors.
As anybody knows who has anything to do with aero-space operations, that is another expression for luck and hope.
Redundancy is hard to plan for on a new untried project but a vehicle for repeat operations has to be designed that way. At least there should be no doubts or “mel” items before dispatch. As we see, maintenance while in space is at best in its infancy.