what are your booting times roughly? I do have the same board and since mojave it takes ages to boot, like several minutes. Also I cannot shut down the system, it always reboots. I usually just put it into sleep mode over night.
Ok, after a few restarts I'm back in the game. :D
All working fine now. Try to select macOS install drive instead of boot macOS from (your drive). Let it load, restart, then select your boot drive. Even with hard restarts, now it works.
may i ask a little off topic question about your audio configuration? I see you also got the VIA chip set in your GA-Z77X-UD3H. How did you solve audio then? The new methods all refer to the Realtek ALC chips.