BLACK/PURPLE (SOMETIMES GREEN) ARTIFACTS IN DISPLAY WINDOW

I've been getting these artifacts in the display window only, that happen periodically. There seems to be no rhyme or reason to when it occurs and when it does FCP locks up resorting to a force quit then affecting OSX and leaving me no option other than to do a hard restart every time. I've been on with Apple Support and a FCPX specialist and they witnessed it, having me do every trick in the book from trashing prefs, trying as a new user, safemode disk repair, etc.
I would suspect video card but it doesn't affect the whole monitor, only the specific viewer window which makes me think it's only FCPX related, but then confuses me in why it's locking up my whole system after force quit.

I am editing off of a Promise R4 (8TB) and using a 6 Core 2013 Mac Pro with AMD Firepro 500. I'm on Yosemite 10.10.4 and FCPX 10.2. I have also done a clean system wipe and fresh install of FCPX and the problem still pops up which bring me back to thinking it's hardware related. Any insight at all would help, thank you!

I'd look at the clips themselves. What created them, what codec are they, what format are they?

Also, did anyone think to trash the render files?

I have also had a similar problem where the timeline is playing, the image freezes but the audio continues. I have to do a hard restart as nothing on the computer responds. I have not noticed any artifacts. Once in a while my left screen goes black for a second or two when I click on the timeline. My computer is the Late 2013 MacPro, 64 G, 3.0 GZ 8 core, and AMD Firepro 700 connected to a Promise R6 (12TB).

I've only had this happen when there's a dodgy connection with the media. We were running a NAS that had a connection problem that was intermittent, and whenever it lost the connection momentarily, we would get a green screen and it would crash. It sounds like the same thing, so I would a) check that the media itself is not corrupt, and b) check that your RAID is not defective and dropping its connection somehow. After doing a clean wipe, etc., it does sound like a hardware problem. I would test the same project with a completely different drive, possibly connected with USB3 or even firewire to test if it's a connection problem (or somehow, your RAID is not serving up the media properly).

Here are some more pics of this issue. All prefs and render files have been trashed in the past. I created a fresh guest user and launched FCP for the first time and the issue occurred right away....

Looked at the clips, all media is fine, happens amongst various libraries at random times. Has happened w/ both ProRes 422 footage and AVCHD coming from a GH4....