So this has been going on for a month and a half ever since patch 3.4 dropped. It only happens when I run two clients simultaneously. Before patch 3.4 I could run two clients simultaneously without issue. I have no upgraded my PC since July of last year so it's not my system specs.

I have tried numerous apparent fixes and even looked into the old thread about this issue that happened to people late the year before last into the early parts of January the next year. None of the fixes in that thread have helped so far.

I am at a complete loss and I'm beginning to think this error is client side as I've said before this issue only started happening right after the 3.4 patch.

But here is my display driver just in case.
Display Driver: NVIDIA GeForce GTX960
Driver Hardware Version: 375.70
NVIDIA GeForce Experience Version: 3.1.0.52

As stated above I've tried every fix recommended for this error from disabelling NVIDIA GeForce Experience while playing to changing values in the Regedit. I am at a total loss as to what could be the problem.