Yes, proprietary systems are so accountable. It only took "the prosecution and conviction of hundreds of [innocent] sub-postmasters for alleged theft, false accounting and/or fraud, resulting in imprisonment, loss of reputation and livelihood, bankruptcy, divorce, and even suicide amongst those involved" before the UK Post Office's proprietary Horizon system was found to be the cause.

So far no-one responsible for the computer system or the prosecution has faced any repercussions.

https://en.wikipedia.org/wiki/British_Post_Office_scandal