What I've seen so far suggest they were just ignorant and victims of confirmational bias etc. You can see that when they won some cases they wrote internally something to the effect of "Final we can put to rest all those concerns about these cases blablabla". So it became self-validating. Also the courts and defense lawyers didn't manage to the see the pattern and in the huge numbers of such cases. Each defendant was fighting their own battle. Also, a mathematician from Fujitsu gave "convincing" testimony they didn't have any errors. A lot was down to lack of understanding of how technology works. The fact that xx millions of transactions were processed without errors doesn't preclude that there could be errors in a small number, as was the case. In this case sometimes coming down to random effects like if race conditions were triggered.