It most certainly still can be a power supply problem, just because your issues may not be attributed to PSU doesn't mean the OP's isn't, both issues could also be cooling issues, have either of you tried reapplying thermal paste on the GPU itself? I am relying on my 15+ years as a hardware technician, so do have a bit of knowledge in troubleshooting issues, which is why I recommended he try a different PSU as that is normally an easy thing to do. I did find one hardware review of his particular power supply and it didn't fair very well in that testing environment.
Just found this advice from another post here.... Worth a look
hey, I encountered a similar problem after screwing with some bios settings after building my system in March 2021:
Corsair 64gb (16x4)
MSI MAG b550 Tomahawk
WD Black 2tb SN850
Sapphire Nitro+ 5700xt
The bios setting that was messing everything up for me was Game Boost. Disable it. I disabled that and the random crashes and reboot loops immediately stopped.
I also disabled resize bar setting. It seems that not having a 6000 series card was causing things to crash for me.
Ohh and pick a pcie mode to lock in. The 5000 series cards are PCIE 4.0 so you can lock it in either pcie 3 or pcie 4 mode. Auto mode causes me problems.
Ohh and it is probably not your PSU. I switched to a 1000w PSU to troubleshoot and was still encountering the boot loop.
Hope this gives you a place to start
@BlkDrgn28 Thanks for finding this other post.
Unfortunately, I wasn't able to find any "Game Boost" or "Resizable BAR" settings in my BIOS.
I did find the option to lock the PCIe mode/version/gen, which I locked at the latest option (Gen3).
Could you please guide me to where I can find the other options?
Edit: I did find the "Re-Size BAR Support", though it was already disabled.
Here is what I found for disabling Game Boost
And good to hear that you found the resizable BAR setting.. from what I had found it is a Motherboard setting more then Video card.