I have a new Asus Zephyrus laptop with the Ryzen 3750H.
It keeps setting itself to 400MHz or .39 GHz to be exact.
It doesn't matter if the laptop is on battery or plugged in.
It doesn't matter what power plan it is on.
The only thing that resets the frequency is to reboot the machine.
Within a few minutes, it ends up permanently downclocking itself again.
I installed the new BIOS that was released 2 days ago. It's still not fixed.
The laptop is not overheating. It doesn't have to even be doing a difficult task.