Photoshop CC problem(s)

I've been running Photoshop CC for years without any trouble. I have
not used it for the last few weeks or so and in the mean time there
have been several upgrades of PS and Windows 10. For whatever reason I
now find that while PS starts OK it now always downloads files in
Camera Raw. I don't mind that but I have not been able to turn that
feature off. To compound the problem, it takes more than 2 hours to
load an image. I don't actually know how long as I give up at that
point. When I load a 30Mb NEF file the image may appear after 2 or 3
minutes but the editing sliders remain locked and unresponsive. The
Windows task manager shows that one processor core (out of 12) is
running at 100% and it will continue to do this until I shut down
Photoshop. Most times I cannot shut down Photoshop in the usual manner
but have to end the task in Task Manager. On occasion I can close
Camera Raw and then I can shutdown Photoshop normally.

I have tried contacting Adobe Tech Support but an afternoon of being
passed from person to person in the hope that the next person would
know about the problem, and after waiting for an hour for what might
have been the last person I gave up.

I then tried the adobe community and quickly received the suggestion
that I should turn off GPU support. GPU setting was previously on Auto
and is now Off. [GPU = GeForce GTX 1070]. That possibly made a
difference, but only minimal. The image still opened in ACR but maybe
more quickly. Fully functioning editing sliders were still not
available even after about ten minutes. One CPU core only, continued
to be fully at work. Some of the graphics memory was in use and there
were occasional barely visible twitches of activity in various parts
of the GPU.

As far as I can tell I have the same problem irrespective of whether I
am using PS 2020 or 2021.

Has anyone encountered or heard of a similar problem and if so what
was the cause/cure?
--

Regards,

Eric Stevens