Could you please run Anvil Pro in loop 3-4 times and see if you have any BSOD / lock-ups? I tried M.2 slot and PCIe slot 2 with adapter, swap SSD's, memory, etc. I have random crashes in 4K high-QD workloads...
P.S: SSDs tested are Toshiba OCZ RD400 and Apacer Z280 with Phison controller. Everybody is testing with Samsung NVMe so I don't know if it's a SSD compatibility problem or CPU / MB issue!