He did the exact same things I did and then some. I found a very old thread, link below, that a guy was having the same issues.
I had to swallow the pill of buying a new card in the middle of this bitcoin crap at the super high prices! It was about 2am my time and I was going to order the new card the next day when I decided to look for a fix. I was 100% sure the GPU was fried and it was too late to return it. I wasn't even playing graphically intensive games either! I had heard that it could be GPU, CPU, Motherboard, PSU. The system would just randomly crash from loading a game, all the way to being in the middle of a game and it crashes. I FIGURED IT OUT!!! I have been dealing with this for over 9 months with a BRAND NEW system I built following all of Linus Tech Tips videos.