Computerphile takes us through some of the technical issues found with the Post Office Horizon computer system that led to several sub postmasters' lives being ruined via false accusations of fraud.

It seems that many of them came from the failure of the system to maintain ACID principles.

From Wikipedia:

In computer science, ACID (atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps.

The speaker is Professor Steven Murdoch, who also wrote a blog post about this that contains examples of the faults he’s talking about taken from the judgement report of the 2019 legal case of Alan Bates and others vs Post Office Limited.