Strange 3D Graphics Issue

Hello,

My MacBook Pro 15" Retina with R9 M370x graphics has been having some strange issues while rendering 3D graphics, and it happens in a variety of applications, ranging from Google Maps to Minecraft. It also persists between operating systems, as I have dual booted Windows 10 with OS X. I have all of the latest OS X updates, I have done a diagnostic check which was clean, I did SMC/PRAM reset, and I took it to the Apple store where they ran tests on it, which passed, and then suggested it was a software/driver issue. They didn't do any repairs or anything. However, I don't think it is a driver issue because it happens across multiple applications and operating systems.

The issue:
Many times I notice strange lines, either black or distorted, appearing all over the place in 3D renderings. They are usually part of the environment, rather than on top. It doesn't happen immediately, but when it does, it usually stays. It may be a heat issue, but I usually keep the laptop pretty well ventilated.

I've seen it happen in Minecraft, Google Maps/Earth, Portal, Unity Game Engine, Goat Simulator, Elite Dangerous on Windows, and X-Plane.

I understand that Macs are not gaming PCs, but given the price of this Mac and the specs, it should be able to handle these applications just fine.

What can I do to resolve this issue? I can't seem to find any software fixes for it. Do I need a replacement card? If I have AppleCare, how can I get one? Thanks for your help.