Hi all,
 
Figured I try and make a post here and see if anyone has seen anything similar or have and ideas? Thankful for any input or suggestions. 

I'm having a serious issue with my GPU, a EVGA 980ti SC, which causes power surge reboots.  

I bought a new computer 4 months ago, bought everything new expect for the GPU which I bought used. For 3 weeks it ran just fine and then i started getting hard reboots without BSODs. 
It varies from game to game, Subnautica kills the comp the quickest. WoT and WoWS killed it in 5mins before GPU cooler reset, now I can run it for an hour. 
Titanfall 2 crashed after 10mins before, can run 2 - 3 hours now.
In Total War: Warhammer 2 the card could run for longer in dx12 mode then in dx11, at least from that I experienced. 
Have never been able to crash it with stresstests, might be possible if pushed even harder though. 
No temp issues that can be detected with software monitoring, when pushed hard in games it goes up to 72C and holds that temp pretty well. 
Everything runs just fine until reboot, no stutter, artifacts, screen issues etc. 

I have tried a lot of things and I will try to keep it as short as possible. 

Clean install of windows, drivers, rollback of drivers
Reset everything in the case. No change
Ran all stresstests I could find. Was never able to crash it this way. 
Changed to a more aggressive fan curve in Afterburner (this improved uptime before reboot)
Change to my old 280x. Runs just fine
Tested another PSU. Same issue 
Removed GPU cooler and applied new cooling paste, the GPU was well maintained and clean. (Improved uptime a lot)
Replaced thermal pads on backplate. No noticeable improvement
Test ran the card in a friends computer. This gave the power surge detected error 

Running low in ideas on what could be tested or done to fix this issue. 
 
Spec 
Intel Core i7 8700K 3.7 GHz 12MB
EVGA 980TI
(2x8GB) DDR4 3000Mhz CL15 Vengeance
2 x 240gb Kingston SSD
Seasonic FOCUS Plus 750W Gold 
ASUS PRIME Z370-A 
be quiet! Pure Rock COU cooler
 
Full load Total War: Warhammer 2
 

 
Idle load screen Total War: Warhammer 2

 
Power supply surges error message during test in other computer

I had this happen to me.
I had to both rma the power supply, AND the video card.
:(
 
So, check the psu numbers, especially in the bios (this is where I saw mine was getting WAY low on the 3.3 rail when it was doing nothing but displaying info in the hardware monitoring section of the bios).
BUT, the video card was also bad. It was doing that reboot without a crash thing, even with a new, known good psu put in.
 
So, it could be a double wammy, or just a bad card.