What I'm saying, is that I think where PHK says "nobody sat down and documented precisely what went wrong", I think he is just wrong.
The guy in the Computerphile video, Steven Murdoch wrote this article:
https://www.benthamsgaze.org/2021/07/15/what-went-wrong-with...,
which has further details of the bugs, e.g.
"There is a window of time between a user printing and cutting-off a report. If another user was to perform a transaction during that window, that transaction may not show on the report."
which is from the long and very detailed judgment: https://www.benthamsgaze.org/wp-content/uploads/2021/07/Bate...
The problem that needs investigating here is the miscarriage of justice, apparently the post office was aware of the bugs at the same time as prosecuting people for falling victim to the bugs, in order to save face about their IT decision.