At a previous job, the team I was on [1] had a dedicated QA engineer (unofficially---he was the only QA engineer that ever worked with our team). Before we got bought, we worked closely with the QA engineer. He had access to the source repo, could compile and test our stuff, and we constantly told him of new features we were working on to give him a heads up. During this time, we were our customer's (yes, we only worked with one customer, who was paying us seven figures per month for service) favorite vendor. Over the 10 years or so of this time, we had like two regressions hit production, and those were found during deployment and we could roll back immediately.
We then got bought out and new management put in. They siloed QA and made it impossible for us to even talk to them about what we were doing. Within a year, we had one deployment fail four times in a row and went from favorite vendor to "utter trash vendor we can't get rid of." Our QA engineer quit, as well as the rest of the team (I was the last to leave). I'm still surprised they still have that customer.
[1] We were the only team having to deal with SS7. It wasn't easy hiring programmers for it, and I think at the highest head count, we had like five members (including the manager when we had one [2], but not including QA, which was "officially" never a part of our team).
[2] If it was tough hiring programmers to deal with SS7, it was even harder to hire managers to deal with programmers dealing with SS7. I think for half the time I was there (over 10 years) I had no official manager and reported to a director or higher in the company.