I can attest to the FACT that Windows 10 IN ITSELF does not cause any FSX issues.
A brave statement.
I have a lengthy post rolling at ORBX forum. The windows 1709 update problem is very real and common amongst FSX-S and P3D users.
One such post follows....
I suggest you pop over to AVSim and check out the comments there, there are 2 threads running, about 180 comments last I counted.
Things I gleaned from the threads,
The fix came out on Tuesday the 5th., didn't work ! KB4051963
Not all computers are effected.
Some users of P3D v4 have the same problems once they install 3rd Party addons, Scenery and Aircraft. For PMDG, it has been a disaster in FSX and P3D V3 & 4, and have been in contact with Microsoft.
In Windows 10 home OS Deferral of update 1709 only lasts 30 days, then it is installed if you like it or not.
Can only defer in Windows 10 Pro, not possible in Windows 10 Home.
Roll back is only possible with Windows 10 Pro.
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I'm glad that you have such faith in FSX and are experiencing no problems, but not very helpful.