Alpha powers off during CS:GO and nothing else?!

Strange issue. Mid-CS:GO match, my Alpha will just shut off. No BSOD or error. Just as if you unplugged it. LED on the PSU goes off and wont power back on until I unplug the PSU and plug is back in. Interestingly, this doesn't occur while playing Overwatch or during the benchmarks I ran (Valley and FurMark). Max GPU temp during benchmarks was 85-86. PSU gets fairly warm but not what I would consider to be "overheating". Event log doesn't reveal any errors prior to shut down.

I still think it's a faulty PSU but I'm a little stumped as to why CS:GO would cause it and not Overwatch or the benchmarks. Here are the specs:

512GB M.2 PCIe SSD 8GB DDR4 GTX 960 4GB GDDR5 i7 6700T 3.6 GHz Windows 10

Any ideas???