I finally pulled the trigger with the iMac 27" 5K late 2015 2TB fusion M395 running Sierra. The computer works well except when it's running the screensaver, I got this red screen once in a while. The display is back to normal when I exit the screensaver. I already clean-installed Sierra but it didn't fix the issue. Should I exchange it? I bought it from BestBuy just 2 weeks ago, brand new. Thanks!