Flickering screen?

I just sent back the N6 that had the screen burn out, I got my RMA device and its on just 5.1 not 5.1.1 should I update it or keep it does it matter? Also this N6 is doing some of the same issues that the other device did before it burned out. The screen has a lot of flickering and triangle flashes but only when I'm using my web browser, also, today I got off of a phone call and the proximity sensor failed to turn the screen on. What's up with that? I'm starting to wonder about these N6's man. Any ideas guys. I think I may need to just flash the s#-t out of this thing