Ryzen 5 1600 overclocking

[Mr_Random_Guy]

So I am overclocking my ryzen 5 1600 which is in a msi b350m mortar arctic mobo with the latest bios. It's stable under prime 95 up to and including 3.7Ghz on stock (1.255v) voltage, and 3.8Ghz at 1.275v. However whenever i put in 3.9Ghz or higher no matter the voltage it justs downcloack to 1.5Ghz and stays there even under load. I've no idea why and i cannot find any setting in the bios that seems to point to this behaviour. Thermals are in check peaking at 62 celcius on the package with a hyper 212 evo under prime95 blend (at 3.8Ghz, 1.275v).

 

Does anyone know how to stop this mysterious downclocking at anything 3.9+Ghz?

 

Thanks in advance