Maybe in this contract they both can have provisions in for poor workmanship and poor engineering decisions. Both for the shop floor as well as the management.
You ship defects, you get salary or bonus deductions and vestments pulled.
Typically quality improvement programs don't rely on punishing mistakes. Doing so results in people hiding mistakes, pressuring QA people to do a worse job etc.
Now if the issue is malice and not mistakes - then you can apply discipline. And indeed most union contracts do still have a process for discipline.
You ship defects, you get salary or bonus deductions and vestments pulled.