This. This. I used to work on safety control systems for heavy industrial applications and it's this. Once the system is running any changes at all went through a whole chain of people. When the change was being implemented I had my supervisor and their manager checking every line over my shoulder before we wrote it. Then test. Then lock it down with a digital signature.

It's not at all like in college/university where you're making changes to your code over and over. Well it is in simulations but that's long before you deploy it. By the end everyone involved should be able to say exactly what every line of code is going to do. This isn't an intern fucking up, the whole team did, and whomever the buck stops with at the top is responsible.