I ran them all again to no avail, but as I said, I had already ran all the QBTools and diagnostic software several dozen times.

On Sunday morning, I removed and recreated the RAID 1 volume and reinstalled Windows 10 Pro.

     -Installed only the required MSI MB drivers from MSI website and updated Windows to current patches.

     -Installed QB 21, restored the company file, ran QB updater and restarted.

     -Disabled all power saving features, installed no further software and began testing.

     -Opened up QB, company file and several company file windows.

     -Checked back periodically every 10m to 2 hours and went through company data, exited and reopened 2-3 times.

     -Repeated above testing steps several times and left on all night. Still running fine this morning.

Today I'll install UPS Worldship and repeat QB testing. If that works I'll install FedEx Ship Manager and do the same tests and so on...

Sooner or later I'll figure it out! So help me!