A final factor that adds to the complexity of the interoperability problem is that Windows itself is almost never the same thing twice. Because of “Windows as a service” the version of Windows 1809 (for example) that you download today is probably not the same as the version of Windows 1809 that you downloaded last week. And the changes aren’t necessarily subtle. We’ve seen major changes in how, for example, OneDrive works within a given version of Windows.
This makes it difficult for all of us to reproduce problems. It can make it hard for you to repro problems reported by your customer sites; It can be hard for us to repro problems that you report to us.
We see this, particularly, when preparing for major upgrades of Windows… say, from 1809 to 19H1. Thankfully, Microsoft has at least returned to the practice of designating releases as “Release Candidates.” But even once a release becomes “final” it continues to change. This is what makes planning to support these upgrades so difficult. We can test with, for example, the release of 20H2 that’s available from Microsoft today. But there’s no guarantee at all that this release will behave the same as next week’s release of 20H2 – And this is true both before and after 20H2 is officially released.