This is not the first RNG bug on Zen 2, I recall after I first got mine that some application or other would quit immediately at startup because rdrand always returned -1, i.e. all 1s. It was fixed with a microcode update.

Do we now learn that they fixed "always generate all 1s" with "never generate all 0s"??

EDIT: I've been unable to reproduce the problem on my CPU, FWIW. It's a Ryzen 5 3600.

EDIT2: OK, update, I can reproduce it with rdrand16, rdrand32 is fine but rdrand16 can never generate all 0s. So my CPU does have this problem!