Oh, well. I guess it'll just be another of life's unknown mysteries. LOL!
I've also been testing Vivaldi as an option and it seems to support a few more of the Opera 12 features I like, such as a progress bar/data in the address bar (as well as a discrete search bar in the address bar).
One feature I sorely miss on both Opera 37 and Vivaldi is the "fit to width" option of Opera 12. Too many forums allow w-i-d-e pics to be embedded in posts necessitating left-right scrolling to read a thread. "Fit to width" handles that problem nicely.