Fault here rests not with defective software but rather with how the Post Office dealt with contracted postmasters when anomalies suggestive of fraud arose. Either by accident or design a blind eye was turned to possibility of glitches associated with the computer system and with underlying records managed by the system. Some Post Office senior-management-tier people were responsible for this mess. The nature of attachable blame may range between indolence/incompetence and direct complicity in a cover-up.
The buck stops at the CEO and board of directors just as it must for the captain of a vessel sunk through ineptitude of the 'officer of the watch'. However, apart from chosen scapegoats all may hide within the amorphous nature of corporate governance.
Perhaps responsibility rests with the shareholders? They elected board members and ratified appointment of the CEO. They collectively are chartering the corporate vessel because they set/approve broad policy for its course.
In reality shareholders of major corporations are merely there for the ride. Perhaps stockholders with major stakes can individually or together exert influence. When shareholdings are distributed more evenly (e.g. as when Building Societies morphed into banks) one ends up with a fairly easily manipulable 'democracy' as in political context.
Obviously, 'democracy' is an ideal state for the titular chairman, CEO and board because of their control over information and setting meeting agendas. Paralleling the 'political class' at Westminster - one such that members across political parties have more interests in common than with their constituents - is a corporate governance class consisting of chairmen, CEOs, and board members, who rotate among companies. Companies of long standing are no longer entrepreneurial or particularly beholden to an individual with emotional and financial stake. Entrepreneurs take a long view. Business school graduates slotted into major companies take the short term self-interest view as seen through bonus culture and share buybacks permitted by USA law.
In the case of the Post Office the hit for irresponsible actions, possibly deliberate malfeasance, shall be taken by shareholders facing a tiny drop in dividend to cover compensation of victims, fines against the corporate entity, and legal fees.
What's lacking is clear individual accountability. When dire matters come to light the responsible chairman, CEO, and board members, may have retired or rotated to a position elsewhere.
How to achieve a moral and legal ethos for corporate entities which demands accountability of individuals is a conundrum. If the Post Office scandal gives rise to a public enquiry then the most worthwhile outcome would be a general framework for accountability to be considered by Parliament for inclusion in statute.