ILL Zen 3 family have some enhancements - try to use Zen 3 CPUs
ILL VRMs on MSI B450M MORTAR MAX are rather weak, so don’t use CPUs with 12 or 16 kernels.
And you’re using AMD Ryzen 9 3900X - bad choice for that mobo.
Also use 2nd and 4th slot when using two memory modules (RTFM, man).
Post
inxi -amz
to be sure.
Message: For most reliable report, use superuser + dmidecode.