That's a known issue with these boards because the board needs to initialize 'new' (added) hardware correctly and that's not always going well. You could start to remove all but 1 ram stick from each socket. Be aware of using the correct ram socket for each stick. There's a table in the mainboard manual. Also, if you have one single ram stick with 'minor issues' you will not be able to boot with socket 1 populated, even with this ram stick populated related to socket 0 and working there.
If you need help let me know.
PS:
Start with socket 0 populated only and add 1 ram stick only. Start it, let it boot. Shutdown. Populate socket 1 and add one ram stick. start it, let it boot. Boot errors can be seen in the log checking the IPMI very easily. Even when you add a PCIe card, it's possible you have to go through the whole initialization process again. The least problems are coming from bios 3801 ... The most problems I had with bios 3202, even with the seller recommending it. Yes, the CPU's are running better with 3202, but it's due to the spectr/meltdown bios patches. Otherwise, I had lots of problems with bios 3202.
What ram are you using ... LRDIMM can cause issues as well. RDIMM should be fine. But once you get these mainboards running, they are playing nice.