Dear Owais, dear Cap Kevin,
I have been running my FlightSim (and GSX) with 2 graphics cards for many years and mostly without problems except that sometimes I got the message "This device (name of graphics card) stopped working for the following reason: DXGI_ERROR_DEVICE_REMOVED. ...". First it happened after updating graphic drivers but I was always able to get GSX back to work. Mind you, different to other Flight Simmers I don't get the mesage in flight or after a certain amount of time but only when I request GSX services at airports and only when close to a gate. So like with Owais, operating GSX seems to trigger a problem. I found that it most often appears when requesting jetways. I tried disabling the GSX jetways and use the default ones but that only helps every now and again and is no real fun. Surprisingly the problem does not occur e.g. in EDDM (using Taxi2Gate).
My setup is similar to yours:
WIN 10, P3Dv4.5, GTX1050TI (for 3 monitors with panels), GTX 970 (for 3 monitors with the pilots' view), ORBX, PMDG 737 and 777.
The error occurs only for one of the cards, mostly the card for the panels. From the pilots view I can still see GSX devices operating and even the jetways operate.
However, I think that our problems are somehow related and like you I would appreciate any help as I don't want to be without my GSX.
Best regards,
Christoph