Is now fix on FSX SP2 too, i have this problem since the update so is not a P3D-specific, denny a bug wont fix it
I can only repeat and confirm it was P3D specific, and it required an update of the Couatl64_P3D.exe, the FSX version is different and hasn't changed. You cannot possibly say what the problem was (we do) and, in fact, what helped us finding it, was PRECISELY the fact that it didn't affect FSX.
So no, your issue fixed in FSX didn't had anything to do with FSX and it didn't work for other reason and fact it works now, is purely coincidental.