Ok, I am puzzled by this issue. ? So far I've had this happen 3-4 times after rebuilding my computer when I bought a new case and cooler.
What happens is:
all my screens turn to black (but still seeing a connected device, they don't show "no signal" prompts)
all fans are still running like normal
RGB effects are still on, but frozen in the state at which the freeze happened
and in 3/4 cases audio output is silent, but one time it made the classic "looping a very short segment of audio loudly" scaring the crap out of my girlfriend.
It has happened playing The Sims 4 and while watching YouTube, but not while idling.
When it happens, I can't shut off the computer by holding the power button, or by pressing the reset button, so I have to flip the power switch on the PSU.
I have Precision boost and D.O.C.P. enabled, CPU temps are low.
The components:
Ryzen 2700X
Asus Prime X370-Pro
4x8GB G.Skill TridentZ 3200Mhz
1070 MSi Gaming-X
EVGA Supernova G3 750W
NZXT Kraken X62
NZXT H440
SSD Samsung 850 EVO (Boot)
SSD Samsung 840
HDD 3TB