gtx 980 Killing Ax860I?

Hi, I've got some questions for some of the more knowledgeable people on the site here. Back in like 2015 I built a new PC with some pretty decent specs:

I5-4690k

gtx 980 (founders edition)(single 8-pin power)

16gb hyper-x fury ram

Ax760i (later ax860I)

However, it only remained functional for about a year before it started to act strange, essentially it started to crash to black screen with no warning at completely random times. (didn't matter if I was gaming or simply watching youtube videos)

I had that power supply RMA'd by corsair (at the price of 45$ in shipping lol) and they sent me back an Ax860I I was happy with this outcome, small fee and I get an upgraded model.

Except after about 2 months it started dying just the same as the last one. Fed up I simply said screw it and bought a cheap EVGA 500W non-modular PSU instead of RMA'ing another PSU to corsair (and waiting another 3 weeks without a computer). The EVGA has worked flawless since I've installed it and the GPU hasn't given me any issues either. So great the problem was solved, but I was never able to figure out the exact cause of the issues. I believe I've narrowed it down to one of three things:

1. The gtx 980 founders edition has some weird voltages only using a single 8-pin connector to get all of its power. This cause it to break the rails on the PSU

2. I merely have gotten very unlucky with corsair power supplies.

3. The gtx 980 doesn't play well with modular power supplies.

(Note:when I asked corsair support about why the ax760I was crashing they simply stated they couldn't tell me)

(Note: Yes I saw that Corsair stickied a thread for RMA'ing the ax860I's for those who own them. I simply want to make sure its actually the power supply before I do that.)

anyways fast-forward to current date I'm looking to do a new PC build but I want to Re-use my gtx 980 as a gpu pass-through for VM's. However, my concern is that, if #1 is correct it could kill yet another power supply and risks damaging the rest of the new system.

TL:DR I need a way to either A: test and that the PSU was actually the root of the problem or B: someone with more knowledge of power supplies can confirm that yes my PSU was faulty and that the gtx 980 isn't to blame. Or lest likely modular vs non-modular made the difference.

Thanks!

Random question: How do/did you secure your PSU into the case? If it's with bolts/screws did you ever check (as per the other sticky) that there was no damage caused to the PSU PCB or any components via over-penetration of the fixing screws inside its enclosure?

That's a known issue and IME that's the most likely way an otherwise stable 760i/860i goes down. Or looking at the flipside I've built about 10 systems with them (and have two here) and never had a peep of misbehaviour out of them. Altho I was lucky to twig the overpenetration issue the first time I installed one and ever since made sure the screws had washers underneath if there was likely to be a proximty problem.

Certainly no specific issues with this particular PSU platform and the 980 in my experience- and assuming you had the overcurrent protection on the PCI-E rails set appropriately, no reason why these supplies would have had any trouble driving the graphics card.

Do you still have the AX860i there? If so it would probably be worth a few minutes peeking through the mounting screwholes to see if there's any evidence of physical contact and subsequent damage.