Most likely it's the motherboard. ASRock is getting nailed right now for unstable XMP and CPU voltages (it's recommended to undervolt a little just in case).
The Asus Prime B650M motherboards they are using aren't exactly high end.
"According to new details from Tech Yes City, the problem stems from the amperage (current) supplied to the processor under AMD's PBO technology. Precision Boost Overdrive employs an algorithm that dynamically adjusts clock speeds for peak performance, based on factors like temperature, power, current, and workload. The issue is reportedly confined to ASRock's high-end and mid-range boards, as they were tuned far too aggressively for Ryzen 9000 CPUs."
The Asus Prime B650M motherboards they are using aren't exactly high end.