Built my first liquid cooled loop recently. No leaks and everything seemed fine. I got the 2080 Super FTW3 w/ Hydro Copper waterblock pre-installed.  I have been using the PC all week to do non-gaming stuff without any issues. I did play Witcher 3 and Jedi Fallen Order for about an hour total on Thursday just to see performance and cooling temps, and they were fine. 
 
Yesterday on Saturday, figured I'd have time to game. I started up Assassin's Creed Origins first. Went into the menu to check the settings in-game and almost immediately both my monitors got covered in artifacts and I had to reboot the PC. After the reboot, I played the game for an hour without any issues. Then I launched Monster Hunter World. I played for about 45 minutes when everything got covered in artifacts again and I had to reboot again. I then downloaded and ran Unigine Superposition and ran that for a while without any issues. I decided to try Monster Hunter again, and again after about 45 minutes everything covered in artifacts and I had to reboot.
 
Both HWMonitor and Precision X are showing great temps. I then turned down the power to 85% in Precision X and played Assassin's Creed again. This time I was able to play for a solid 2-3 hours without any issues before logging off for the night. 
 
A couple other notes that might be useful:
 
* I am using dual monitors (but only 1 to game with). The main one is DisplayPort. My second monitor only had DVI so I had to buy a DVI to HDMI adapter for that one to use with this card. 
* I am using a PCI-e riser cable to mount the card vertically (the card is literally too big to sit horizontally in my Lian-Li O11 Dynamic case). I have ordered a new cable to test in case that is what's causing the issues. 
 
I have not overclocked the card at all. Any thoughts here or should I just go ahead and start the RMA process (assuming the new cable doesn't work)?

What were the temps before and after you changed the power target?

GTXJackBauer
What were the temps before and after you changed the power target?

Around 54 C under load before reducing power target. Around 50 C under load after. 
 

Cool GTX
What PSU & is it new
 
Using two separate power cables to the GPU ? - not one PCIe cable with the jumper to the second port on the card
 
Remove the OC from the CPU & RAM ... does it do the same ?
 
Look forward to your update after the new riser cable is tested ..... try to avoid any tight corners/ bends - I like to use a sharpie to make a nice radius

Corsair RM850x and yes it's new. I believe it's using the jumper method. One end is connected to the PSU and the other end splits off into "2 branches" if that makes sense. Here's a picture: 
 
CPU and RAM aren't overclocked. Haven't overclocked anything in the system yet. Since it's FTW3 the card itself should have some type of factory OC on it. 

That cable branching into two is still a single cable.  Try using two separate cables to power the GPU and go from there.

I have two evga rtx 2080 super FTW3 hydro copper and i have been running the cards for about two weeks with no problems with a +970 for mem and + 80 for the core with the sliders voltage ,power, gpu temp maxed out in precision x1 when gaming for hours my temps are top card is 36 degree and the bottom card 37 degree but not on riser cable and I have pci express power cable to cards with no jumper all separate from my  power supply.

No luck. Tried a different PCIe riser cable, and per suggestions used 2 different power cables from the GPU to the PSU. 
 
Ran Monster Hunter World, was fine for half an hour then I realized I had set Precision X to 85% power the other day. Set it back to 100% and got artifacts within 10 minutes. 
 
Looks like I'm going the RMA route. 

EVGA support suggested to first check my 12v rail voltage in the BIOS. The support tech mentioned that the 20 series is very sensitive to any fluctuations. I see it fluctuating between 12.168 and 12.240 every now and then. Shouldn't this small of a fluctuation not be an issue? I have a pretty decent PSU (Corsair RM850x), and I can't find any info on whether this small of a fluctuation is normal in it or not. I've also seen lots of posts online mentioning that voltage fluctuations could cause crashes / system shutdowns, but artifacting is typically still tied to the GPU itself. 
 

Replaced the PSU and the new one is steady at 12.168. 
 
Managed about 45 minutes of MHW before artifacts again. Submitted another ticket. 

Fishphoenix
Replaced the PSU and the new one is steady at 12.168. 
 
Managed about 45 minutes of MHW before artifacts again. Submitted another ticket. 

Let us know how it goes.

Thanks for the update

Replacement arrived yesterday.
 
It's leaking. Not my fittings either. Leaking from somewhere there shouldn't even be water. Going to call them tomorrow. This is getting ridiculous. 

That's a bummer.  I'm sure they'll take care of you with an RMA.

Curios to know if u got a good one. Evga hasnt responded to my rma request so i went and ordered another in the mean time it should be here today. Did your 3rd block work? I hope my 2nd one works if not both go back and im going with ek which would be a bummer because ive stayed evga for 10 years now and ive never bought anything else because theyve done well by me.

Ill surely update tonight if a new block fixes my issue its insane to think qa let a block go that clearly has a gap you can stick a quarter through.

Thanks for sharing Fish. I am thinking about jumping into building my first liquid cooling loop as well.