It was and is a very complicated system - the post office that is, their IT system has to interface with many different external systems.
Problems were reported from day one, they were ignored from day one. The Royal Mail knew there were problems but when they were prosecuting individuals they kept that information back from the defence.
I still think that before people get sent to prison there should be proof that the system works flawlessly. and if the prosecution doesn't provide it the defense should demand it. It sounds like postal executives are the people who need to be locked up.