I presume you are using the latest BIOS.
I was sure it would of been the VDDP voltage but you have it up there high already so should not be it now.
I ran into issues running 1900FCLK with too high VDDP not wanting to boot (why I went for low values), same thing with too high VSOC gave memory errors @ 1900FCLK.
But your not up there @ that speed and I've seen other need small increases compared to stock to get their stuff to work.
VDDP 1000mv , vsoc should not be an issue as you have it.
Have you tried LLC settings? Might be CPU voltage related. Maybe a slight LLC boost for Vdroop might help the issue?
You have PBO AUTO/disabled? PBO isn't guaranteed to be stable so best to leave that OFF when you troubleshoot ot try LLC as I suggested to get a slight voltage boost.
Offset might do it as well but isn't really recommended as your CPU might overvolt too high then.
There are a few diffrent voltages to try avaiable like CPU VDDP, PL18 and then DDRVPP or what it was called @ 2.500V stock?
There are things like procODT & the Bus Strength values that might need adjustment. Though they are usually to fix stability/errors not random reboots but doesn't hurt to try if not finding other stuff to fix it.
Gigabyte X570 AORUS XTREME, Ryzen 7 3800X 4.45Ghz, 4266/1900 MEM/FCLK, 220.127.116.11.76.tRFC 650 1T 1.58V
4x8Gb Kingston HX434C19FB2K2/16 3466C19 1.2V (Micron E-die 16nm)
OLD: Biostar x470GT8 Ryzen 7 1700 @ ~4.0Ghz CPU, 3200Mhz RAM ...