PC crashes/freezes while doing nothing at times

[Vorikx]

So I've had this problem for a few weeks now. It'll be at random time (whether I'm watching a video on YouTube, playing a game, or streaming) that my PC will freeze and my keyboard light and webcam shuts off, but everything else stays on but unresponsive. The PC itself remains on, all my monitors are on, the mouse light is on, but nothing responds. The PC never fails stress testing (real bench) and passes memory test with no errors. If audio is playing during the freeze, the audio will screech super loud throughout my headphones nonstop. I have to force shutoff the PC, restart button doesn't respond either.

Specs: I7-6700k (was OC'd @ 4.5ghz, just reset bios after last freeze 10 mins ago)
ASUS Z170-A Motherboard
2 GTX MSI 970's (SLI)
16GB of PNY Anarchy RAM
850 watt EVGA Bronze Power Supply
Hyper 212 Evo air cooler

 

[IgorNew]

Ok here is your solution.
You have unstable oc.
Keep your vcore and lower your cpu oc to 4.4Ghz or up your vcore a bit for sake of safety don't go with vcore over 1.45 (that is max i feel safe about someone will say 1.325 someone will say 1.5).
Then use cpu stability test like aida or prime 95 to test cpu stability.

 

[Rexer]

So, did you down clock the bios? Did it solve the problem? What was the result?
Have you tried anything else like swapping the PSU?
Power is suspect, too. Doesn't always show up under stress test. Had a Corsair RM 750 gold that was bad from the onset. It finally died completely and when I checked online with Corsair, found out it was on recall for a faulty auto-fan setting. Would run fine till it warmed up and overheated.
I had a battery back-up unit die once. That totally fooled me. It would randomly shut down till it died one day. They're design to check power but the board went out, not the battery.
Motherboard with a bad cap does random shut-offs. Check the tops of the capacitors (the little cans) to see if the blow cap hasn't expanded. Look for burns anywhere. Sometimes they're hard to see.
Reseat your hardware, unattach and reattach plugs and ram. It cleans dirty contact points. Faulty contacts will do random blackouts not always seen.