It's the cost of doing business. Some times, things go wrong. Some times, it's really expensive to right the wrong. But, way better I caught it in the shop while the doors were still sitting on a cart assembled rather than after they had been sized, bored, finish sanded, painted, and hung in the house. That would've been expensive beyond financially. Loosing face with an account can be difficult to remediate. Bad product caught in the shop is a problem. Bad product caught in the field is an absolute nightmare.
That stuff used to REALLY make me angry. Then I learned to get better at my job, and to also accept that I am human. As much as I want to be a robot and be doing things perfectly, that is not a realistic expectation. An extreme minority of people are capable of that, I ain't one of them. Sometimes I screw up, and sometimes my guys do. Most of our employees are not capable of operating the way that the we as employers do. We see things differently, we interact with them differently. Most of us are driven to succeed, (or at least not fail), and obsessed with what we do. Probably to our own detriment.