I'll say this just incase people overlooked it or have not tried this as a last resort... no guarantees or anything but just my experience.
Backup everything you need and then do a clean Windows install, set your PC up to use c-states and install the barebone drivers with AMD Chipset stuff. Install Ryzen Master and no other monitoring software or additional programs and see if you have similar issues.
When I had my AMD build, I noticed similar issues when I would even have just Discord in the background. Discord even doing miniscule stuff such as I guess checking if people are still online is enough to not trigger idle status and boosts happen. Having just discord open increased idle temps iirc. Now I think about it, if you install Windows with that auto online account stuff, it's probably sending so much data home constantly that having the cpu idle would not happen. Use an offline W10 account (unplug Ethernet on install) then run O&O Shutup10 to disable call home stuff. If all of that still fails then yes I guess either the CPU or motherboard is weirdly faulty.