Fascinating.
Maybe it's an Orbx thing. Did you or your friend ever try disabling your Orbx scenery to see if that was the culprit? I have tons of Orbx scenery and other stuff installed, both free and paid.
Not long ago I decided to just go with "it is what it is". Maybe I'll just go back to simply accepting it. I know others, besides me, you, and your friend, have experienced the same thing. There are a few posts about it elsewhere on the Internets. But no solution, or even a confirmed culprit.
I do like to hear you say "Using SSD, going to Win 10, sim "repair," reformatting and other such things won't fix that (don't waste your time and trouble)." I'm really not looking forward to doing any of those things. But still might if for no other reason than to clean up my computer.
(Sometimes accepting a challenge like this -- finding the culprit -- can be fun too. LOL.)