Can you try lowering your max cache ratio from bios to 42? It is set to "auto" by default and this makes it run a bit faster (NB frequency on cpu-z memory tab). Also I would recommend running VCCSA=1,15V and VCCIO=1,10V for ram speeds above 3200MHz, something lower like 1,10V and 1,05V respectively might work, but having both at 1,00V with those memory speeds is not really recommeded, since VCCSA defaults to 1,05V and VCCIO to 0,95V at the SPD speeds (2133MHz).
You could also downgrade to bios 0802 since I have seen some people mentioning that the bios 1003 has made their memory overclocks worse.
"Tried increasing SA and IO in 0.10 steps up to 1.360V each" is missing a 0.
I tried upping the voltage in 0.010 steps up to 1.360V, from 1.000V for both SA and IO, just like you said.
Every time (if the system booted) ran MemTest86 until errors were found. Then up the voltage again.
That would be almost a full day just doing that 😞
All I am seeing are Volts and decimals now.
later edit: I need a couple of days to forget the "horror" and will try from 1.360 backwards.