Could try updating drivers or using a slightly older one and maybe updating the GPU bios.
Other than that I would say return and replace.
I'll try some older drivers when I get the time, I am beginning to think it is a driver issue TBH, benchmarks its totally ok, zero issues, just gaming... it's a strange one...
I just don't get how I can run so many tests and it runs totally fine tho, 10min gaming...... higher temps and downclocking..... I've tested far cry 5, far cry new dawn, sleeping dogs, ride 3
I'm ruling out bad air flow, or added cpu heat, my system doesn't get hot, it never has, Hell I even crossfired 2 7850's and the temps wasn't too bad, and that rules out a bad psu too.....
I'll check to see if there's a new bios too