OC problem

I just noticed in your first post you use Windows 7.

While drivers are supplied for other Windows versions, only Windows 10 is officially supports Ryzen.

This may be related to your failed OC.

What are the Windows crash dumps saying failed during stress testing?

You never said what your "small OC" was. Ryzen 7 processors hit the OC wall at or just below 4GHz, with sane voltages.

No idea what other components are being used, the PSU in particular.

I think hes going to at least be using the AMD Wraith Spire cooler, which is actually pretty decent so temps shouldn't be too much of a issue.

I've tested the K4 with that RAM kit and a Zen 1700, Maximum I got from the CPU is 3.9GHz @ 1.38v and 3066MHz CL14 @ 1.35v. This was done with UEFI 2.5 I haven't tried 3.0 yet.

3.9GHz on any Zen chip is not a small OC it is pushing the lithography of the CPU extremely close to it's current limits. Try 3.7GHz with 1.25v as a starting base. You should also be able to run that kit of G.Skill RAM @ 2933MHz without any issues.

Check to make sure you have the RAM installed in dual channel mode (banks A1+B1 or A2+B2)
Run HCI memtest with enough instances open to fully utilise your RAM and leave it for at least 2 hours, see if it reports any errors.