@foone @foone what are your core temps and clocks like in hwinfo? Heatsinks all snug? All internals unobstructed? Checked the board for any spicy caps? When you tested RAM, was it a matched pair? Anything overclocked or undervolted? Tried another PCIe slot for the GPU?
Worst case the motherboard is just dying, I had an X99 Asus board which was notorious for eating CPUs (which mine did, while simultaneously FUBARing itself). That's probably a niche edge case though 😅