It looks like I might have accidentally fixed my problem yesterday, because I had no BSODs for over 26 hours. And I have no idea, how. Things I did in order:
- After shutting computer down I disconnected my entire setup from outlet. I removed heatsink and washed old thermal paste with isopropyl alcohol and some cotton pads (or whatever one calls the round thigies used to wipe makeup off). I removed the CPU from the socket and washed it too. I had to wash the bottom side too, as bit of thermal paste got between the pins - I used sewing needle to remove it. I also cleaned the socket for good measure. I reassembled it all back with new thermal paste, Silentium PC Pactum PT-2. I took the oportunity to also move some cabling around and make sure that all connections are solid.
- After power up it turned out that BIOS was reset to factory settings. So I switched XMP profile for memory back on, set the CPU fan to full blast, adjusted boot order and then set the CPU frequency to 3850MHz. Save and exit, and BSOD as soon as Windows 10 loaded. Bug Check 0X162, KERNEL_AUTO_BOOST_INVALID_LOCK_RELEASE.
- After reboot I went back to BIOS and disabled Precision Overdrive. Reboot, another BSOD. Don't remember, what it was exactly.
- Then after reboot I selected "Load optimized defaults" from BIOS options and redid changes from point 2, sans changing any clocks. Since then I had no problems. There were two updates to MS Defender since then too.
So now I don't know, if this was solved in BIOS or by my messing with MB and CPU. Or by those two updates. Or by magic. I hope this lasts. If not, I'll inform you all here and on Reddit...