OK, I got with Apple Tech Support on chat again and the tech suggested erasing the drive and data after backing up by using command + R at start. I did that and then reinstalled the 'freshest' Big Sur which worked fine. I then reinstalled my apps and data from backup. Worked flawlessly. One thing though. I found it hard to believe that this problem was found during update testing and fixed. A bit disappointing that. Also, even being tech savvy taking such a drastic step makes me feel like I'm jumping out of a perfectly good airplane (something I won't do) and when I downloaded the chat to be sure I didn't miss anything I noticed it didn't download perfectly... something else for Apple to look at fixing. Luckily, being a bit 'anal' maybe, I copied the crucial part of the chat before downloading and saved it as a document which I printed out and also didn't need but it's something many would I'd think. Soooo... make sure you got the steps down before ending the chat or copy it out some other way besides downloading. It seems the numbered lines in the steps the tech sent were what did not print out which mostly gave me every other line. Example: "1. From the utilities window in macOS Recovery, select Disk Utility and click Continue." Came out in the download as a blank line and the 'Continue' which wasn't very helpful if you didn't know what you were doing already. Of course, there is always the Apple Store if you can get in! : ) Good luck! I hope the next update goes a bit more smoothly... this was like rebuilding the whole engine of the car from scratch when I only wanted to change the spark plugs. Make sure you know what you are doing before you attempt this!
