Thank you for the response.
So I have one machine in particular I am testing with. About as vanilla a machine as I have. Originally it offered me version 20H2 as an "option". I accepted the update and it failed, reversing Windows to it's previous version. Then I attempted to install from the 20H2 media. Again it failed. Lastly, it now has said a "required" update is available - 20H2 - which I accepted and that update failed.
Like I said, it doesn't matter how I attempt to do the install. Since version 1909 the installation of updates has been awful. A huge time sync for me and very interruptive for my users. There's nothing unusual about my environment and to expect the user community to help each other and fix this is totally unacceptable. ***Microsoft needs to get off the stick and get this fixed!***Microsoft - I'm in the book. Give me a call.