Hi,
I have a similar problem.
Yesterday I installed a really fresh Windows 10 Pro on a new SSD and installed P3D v4.2 too. All drivers and SO updated to yesterday.
Then install in this order: Toposim mesh, ORBX Global, ORBX Europe LC and PMDG NGX. I fly a short 1 hour flight and all correct.
Today I install GSX and when undock any window like PMDG ND or PFD, P3D ATC window, etc. and move to other monitor, fps low to 10. If undock PMDG ND on the principal monitor, no low fps but the ND undocked stay freeze; if return to dock the image move again.
I tried to uninstall GSX and the problem disappears.
Then, I can't use GSX becouse my frames low to 10 fps in all aiports and with all aircrafts.
Please, can you help me?
Thanks and best.