Yeah as mentioned in the first post I had the same crash to desktop in Gears of war 5 and control. GTA V is just the easiest one to test as it happenes quite quickly where as the other it could be hours until you get a crash to desktop and I cant play for hours each time to test. That makes GTA V the easiest way to test that its still happening. It could be the combination of hardware yes. The company I purchased from thinks it may be the 3900X CPU but I personally think its either that or the motherboard and as you mentioned it could be a compatability issue with the hardware. If I do return it though they have no more 3900x in stock so no idea how long I would have to wait which is why I was hoping to find the cause myself and fix it but iv literally tried everything I can think of including all the suggestions in this thread.