I've been trying to set up a Ryzen-based system, but having all kinds of trouble with the RAM. The first motherboard I had (MSI X370 Gaming Plus) wouldn't run any memory settings other than 'auto' (including manually setting 2133MHz), with any of the three RAM kits I have, including one that's on the QVL. Thinking it was some weird motherboard issue, I bought an Aorus X370 Gaming 5, which worked OK for about 24 hours before that has also slipped into the same behaviour - no memory settings other than 'auto', including manually setting the same clock as auto, will boot. Both motherboards are running the latest BIOS, and all other settings are stock. The only thing in common is the CPU. Does my CPU have a defective memory controller?
I would say it is likely there is a fault somewhere in the CPU yes.