How often is common to you? I've seen it happen plenty, and not just with Python. Even Go, which has a reputation for maintaining backwards compatibility, had bugs that caused breakage on patch releases during the go.mod transition. Even if breakage happens rarely, when it does happen it causes unplanned work. I'd rather be deliberate in when I choose to upgrade so I can plan for issues.
As mentioned, they weren't bugs but multiple planned breakages.
IMHO, Python devs learned the wrong lesson from the 2 --> 3 transition. Should have been, "minimize big breaks." Instead they learned, "make lots of small breaks spread out evenly and avoid X.0 releases." The result is that planning around deprecation (always be breaking) is untenable for enterprise-style development.