You might want to try reducing your memory clock a little, as there are no supported 4x16GB DDR4-4400 configurations on the
memory QVL (the 4 stick configurations have a 4 in the "socket support" column). Getting 4 sticks of overclocked RAM to work can sometimes be much harder than 2 sticks.
I would start by running with DOCP off for a while (running at default JEDEC SPD speed, probably somewhere in the 2133-2666 range), to see if that is stable. If that works, try DOCP but with the rate reduced to 3600, and see if that's stable. Your memory is probably similar to mine (4x16 Ballistix DDR4-3600), but from a higher bin; 3600 is the fastest QVL speed for a 4-stick Crucial/Micron configuration. I'm having good results with the Ballistix DDR4-3600 on the Crosshair VIII Extreme (also a X570S board, the bigger sibling to the Dark Hero). If 3600 works well, you can try to push it faster. You might also try slackening the timings a little (e.g. going to a higher CL number, etc).
You could also try running with just 2 sticks for a while (and swapping between the pairs), to see if the RAM is stable like that and probably just needs manual tuning to get it working as 4 stick. The problems might not be RAM related, but trying to run 4 sticks super-fast (beyond 3600 on AM4) is an obvious source of potential instability.
