The problem is solved … and it was a new one for me!
I finally noticed that only one file was affected. Then I noticed that the right viewport was corrupted with VERY ODD values, image below. What was WEIRD was that it affected every viewport, which is why I didn’t catch it.
The Right view camera ‘X location’ is in another galaxy. This is a corruption.
The four view reset didn’t fix it the numerous times I tried. I had to manually delete the Right view, THEN do the four view reset.
So, one rogue camera x-location value was able to damage ALL four viewports. Who knew?