Yeah I got exactly the same problem, and I think its the GPU. Do you think it could also be your Watercooling? I got the Kraken X63, and I'm not 100 % sure if its not that.
But if its the GPU, atm (at the moment) its very bad because as you said the shortage.
I bought it on Amazon, and they can only give me the money at the moment.
I would like to buy either a 3080 or 3080ti, but because of the Shortage, Prices are very high atm.
I can RMA my GPU until April so I will wait and see, if i can gather a cheaper 3080 until then and return my RTX 2070 Super for the money, no other idea right now.