There has not been a single major patch without a critical issue since Endwalker.

[Arzalis]

Software development of a mature product.

Source: I work in software development for a mature product. Bugs happen.

I work in software dev too.

Bugs happen, of course. If they consistently happen across multiple major releases, then something needs to change. At that point, your testing methodology is flawed and needs to be re-examined.