I understand your situation, Quality of everything degraded over time.
Last week I bought a MSI mobo and trying to fix a issue - One of a Pcie slot didn't detects my sound card after cold boot, however it works when I swap from other pcie slot and softboot or reset it.
after troubleshooting everything for last 3-4 days, I reached to the conclusion something isn't right with Bios code.
My situation is even different , what to do when you don't 've service center in your city, taking it to 70kms is these times is another stress moreover it's BIOS issue which can't be resolved with a replacement.
Such poor programming skills.
just because of this issue I need to plug it in other Pcie slot near my GPU which is now running 10-12C hotter.
Most likely your problem should be resolved with new mobo, if not then we'll restart the loop from GPU