Question PC freezing/shutting down under heavy load

[LikeABossNT]

Hello, this is bit of a long one so tl;dr is at the bottom.

CPU: i7-13700k
GPU: started with GTX 1080 Ti, swapped to RTX 4070 Ti Super
PSU: Deepcool 1000W PQ1000M, and 850W XFX used for testing
RAM: DDR5 32GB 5600MHz
Mobo: Gigabyte Z790 GAMING X AX
OS: Windows 10 Pro 64bit

This all started about a month ago when I wanted to start gaming again. Every time I would boot up a more demanding game the PC would freeze (fans still running but nothing happening).
Temps were fine so after bit of searching online I swapped my PSU for my old one and everything started working normally.
I sent my main PSU for repairs and after 2 weeks (now) it came back. Apparently they had ran a bunch of tests but everything was fine and it didn't need repairs, so I put it back into my PC.
My PC started freezing again so I swapped back to the old PSU and prepared to send the new one back for repairs again, but here comes the twist:
With the old PSU that was working fine before, I started to experience the same crashes as with the new one. After some attempts the freezes started to be more varied, changing between a freeze, shutdown and reboot.
At this point I'm very confused and have no idea what's happening. Maybe it was the mobo/cpu afterall and I was just lucky for the few weeks I used my old psu?
Tempts are still fine (35c idle, 80-85c 100% load).
During the 2 weeks with my old PSU I played a lot of Final Fantasy XIV, which isn't the most cpu intense game, but it was fine even with +10h sessions.
Back when the issues started I had a GTX 1080 Ti but I bought a RTX 4070 Ti Super few weeks ago, so at least I can rule out the GPU as a culprit for these issues.

tl;dr:
Every time I started a more intense software/game, my pc froze
Swapped out my PSU and things started to work normally
Got my PSU back from repairs after few weeks and the issues came back, but after swapping back to old one the issues remained and instead of always freezing it would occasionally just shut down/reboot.
At the start used a game to test it, but now for troubleshooting I've been using SilverBench.
Temps are fine. Got a new GPU so that's fine.
Event Viewer has critical errors, but they only say "The system has rebooted without cleanly shutting down first." or "unexpected shutdown"

 

[Lutfij]

I sent my main PSU for repairs
You mean RMA, right? Because there's nothing worth servicing in them if you're on a warranty scheme for the unit. You get a direct replacement for having a PSU end up faulty or failing during it's warranty period.

BIOS version for your motherboard?

Did you run DDU when you swapped the GPU over from the GTX1080Ti to the RTX4060Ti Super?

 

[LikeABossNT]

I sent my main PSU for repairs
You mean RMA, right? Because there's nothing worth servicing in them if you're on a warranty scheme for the unit. You get a direct replacement for having a PSU end up faulty or failing during it's warranty period.

BIOS version for your motherboard?

Did you run DDU when you swapped the GPU over from the GTX1080Ti to the RTX4060Ti Super?

Yes sorry, meant RMA. Can't remember BIOS version, but I did update it somewhat recently. The issues remained the same before and after GPU swap, but yes I did a clean install for drivers.
EDIT: checked and updated BIOS, it's version 11b now