X670E Taichi randomly resets

Failed contacts?!

I think I have finally found the REASON for the reboots. But probably not the culprit.
Following advice in another forum thread where someone saw the same behaviour on a different board I started testing with OCCT:

CPU Test
AVX2
Small data set
Extreme mode
Start at cycle 1
Threads: advanced
Testing physical and virtual cores and starting with core 0 and 1
cycling cores every 10 seconds

After a couple minutes I see physical core #4 reporting problems. Sometimes that core has issues on the first pass, sometimes it takes a couple passes for errors to show up. I think that's what is making it so inconsistent. But now I can at least start tracking down what is causing those problems. Maybe the core is just physically defective on my CPU.

I have a new PSU on the way since redoing my cables seemingly helped a little bit.

Errors occured at stock memory speeds (4800) and PBO on auto, since I just loaded defaults.
I re-flashed back to 1.11AS06, cleared CMOS and explicitly DISABLED PBO. Memory is still at stock speeds right now. Yesterday it completed 6 hours of OCCT and no errors were reported. Gaming was also stable with no reboots.
I left the system running overnight and today in the morning there were no errors. Since then I started yet another run and no errors. Maybe leaving PBO on auto enables a boosting behaviour that causes a single core not to be stable and when that core does something crucial and encounters and error, the whole thing just reboots?

Would be great to hear some insight on this theory. Right now everything seems fine. PSU swap will commence either way, though. This one is out of warranty.

Your hunch that PBO2 is causing the crashes might be the correct one.

Currently PBO2 could maybe lead to over voltage being supplied to the CPU.

It depends on frequency and temperature of CPU.

Leaving of PBO2 should be better for stability, also check latest bios/firmware updates, there are found problems with older bioses that could even blow up these processors.