Thanks to everybody who responded. The following might help somebody in the future . . .

I did a Windows RESTORE. This takes the operating system back to a point in the past, before updates, etc. When this is done, Windows 10 gives an information screen regarding what will be affected by going back to that point in the past. Guess what was affected . . . BIAB, RealBand and RealTek drivers.

Long story short - did the restore, everything worked as it did before. Got the final mix, made 3 redundant backups and the saga ends.

Thanks again.