PC random black screen, doesn't come back

I bought a Samsung Odyssey G9 and Nvidia 5070ti about a month ago. Monitor came first, works great. A week and a half later, I get the GPU. Case is 1mm too small for GPU, so I buy a new case (great start). Now my video (DisplayPort) and audio (USB to an interface) output drops, regardless of activity, then my fans ramp up. Then only solution I've found is a manual restart.

My PSU was almost a decade old anyway, so I bought a new one just to rule that out (again, great). Event Viewer and Reliability Monitor show kernel errors related to Nvidia drivers. So I switched from the standard driver to Studio to rule that out, same result. So I updated my mobo BIOS, same result. At that point I felt comfortable calling the GPU somewhat defective and returned it (had to pay for shipping, $171, again great). Replacement GPU arrived yesterday, and my outputs just dropped again and needed a manual restart. This time I'm not seeing any error codes however. I'm losing my mind, I really need help from a tech wizard.

Win11 Pro Gigabyte Z490 Pro AX Intel i9-10900F RAM 16GB (I think Vengeance) Nvidia 5070-ti Corsair RM1000X