When I had FSX the issue was with the shadows, that this program insisted in changing my personal setting.
No, it happened only on a very specific case:
You were flying over an FSDT scenery, which turn on/off shadows over a certain height, because you wouldn't see it anyway, but it would result in significant fps savings, especially if you have many AI planes. This is NOT happening when flying outside an FSDT scenery, of course.
The shadow setting is READ from YOUR existing setting when the sim starts and, it's turned Off/On (depending the eyepoint Altitude) if YOUR existing setting was On, and it's always Off if YOUR existing setting was Off. Again, only when flying over an FSDT scenery.
However, if you flew over an FSDT scenery, over the threshold altitude to turn shadows Off and you QUIT FSX in that moment (not crash, you must explicitly Quit), it will FSX ITSELF, which will save the current shadow setting it has in memory, so they will be Off at the next startup.
So, it was a very unusual case: you had to start an FSDT scenery, go to some altitude and then QUIT from FSX.
How I resolved? I created a batch file that upon every FSX startup deleted the current .CFG and copied a fresh "new" one (the one I trusted with my settings) to its place. Never again I had issues.
Totally unnecessary, if you wanted to have your airplane cast shadows setting unchanged, you simply had to turn it on once, and don't QUIT from FSX when you are flying OVER an FSDT scenery.