I has in practice 4 Gb gpus on WIN10 and mined without problems as I told early

But maybe your monitor is connected to the motherboard video... Not on the mining card...
No, my monitor connected to the first video card because my processor no has integrated video
What and where are you mining?
I tried to mine eth in ethermine and i tried to mine in nicehash - a lot of problems and restarts... And some of mine RX480 are with a speed 7-8 MHs
You could also could have hardware problem. Exchange first card with some of the others and tell us which card fails after that.