The core problem is that it is a people business with varying degrees of quality control. Early on in my career, we saw significant problems with complex installations which led me to do a data driven analysis of the problem. From that data, we developed "Design it right, Build it right and Keep it right" program.
The biggest issue was misconfiguration and setup. What we found is that no one person was mistake proof. So sales/field designs had a review-check from an architect level person in-house. Implementations had automated configuration validations. Production also has to have an always on monitoring and operational response. Even small configuration changes force revalidation.
Some of these things have costs which can affect margin, however, the cost of mistakes not only affected margin, but also customer confidence and loyalty. By leveraging automation, we could scale operations without scaling costs. By formalizing processes, procedures, and training, we could make human costs more efficient as well. For each business, you have to assess your own strategic investments but the right investments create differentiation and scale. For me, it also allowed me to sleep better at night.
For some of the issues described in the original post and subsequent replies, we addressed those by developing clear standards of how things were done. Relying on senior people to help define standards and train junior people improved even the senior peoples' performance as a level of status-responsibility increased job satisfaction. Moreover, they recognized that they were modeling best practices in every build and could lose that status if they let their own performance slip. It also meant clear accountability when mistakes are made. Peer scoring, self-scoring and postmortems allowed for people to have a hand in self correction before it becomes a career event.
At the same time, we had to mentor project managers and leaders to communicate perceptions of poor performance. The focus being on the performance not the person but in the end of the day, if someone was perceived as slipping and nobody confronted the issue, then problems perpetuate and the individual just starts to feel a lot of passive-aggressive behavior. For people to correct, they need to recognize they are being fairly held accountable. Moreover, having clear, fair communication also puts you in a better position from an employment law standpoint.
Naturally, any one circumstance can have individuals and personalities that can end up being unpredictable. Avoiding honest communication never yields a better result however.