Despite Apple saying that the Sierra update 10.12.2 would resolve the video/graphics problem, it did not, and nor does update 10.12.3. I bought the machine for work and am told by the Apple Store at which I bought it that I have to return it and wait a month for a "possible" repair. As the fault only occurs on a random, and sometimes infrequent basis, it could takes weeks for the repair shop to even replicate the problem. That's going to be more expensive than throwing the machine in the trash bin. Apart from the extended wait, I'll have to wipe the machine, find another computer to use in the meantime, then wipe that, then re-install everything on the Mac once again - in the hope that it just might work. Beware!