iMac 27" 5K Late 2015 screen artefacts on shutdown

This is the link to report issues:

http://www.apple.com/feedback/macosx.html

I submitted feedback to Apple re this screen artifact issue & referenced this thread.

I too submitted feedback to Apple (yesterday) re this screen artifact issue - sometimes - on shutdown of 'Macs' after upgrading to Sierra (no problems before on same machine for months wih El Capitan) & referenced this thread.

I had the same problem on my iMac.

Power Supply has been changed, logic board has been changed. No results.

Apple has renewed my iMac and the problems was still the same with a new computer.

After the installation of El Capitan I had no problems so far.

Hope it stays like this.

So this issue is a software problem I guess.

After my initial report on this issue last month, now curiously shutdowns are normal again. Done absolutely nothing special in the meantime... Finger crossed.

I though it might have been fixed too but bam back again after the latest Sierra 10.12.2. (and yes it is a software problem)

Widespread 'graphics issue' - http://www.macrumors.com/2016/12/02/new-macbook-pro-graphics-issues/

I was unfortunately singing victory too early. I'm a release back (10.12.1) compared to you and today it appeared again. Completely random as far as I can tell at this point.

Guys,

Any news after the latest update?

After one week working with downgrade to El Capitan still no problems.

My solution was downgrading to El Capitan.

I have updated to the latest Sierra release, and since that was released I haven't experienced atrifacts in shutdown at all, I have shutdown about a dozen times and would have seen it during at least half shutdowns.

I am still seeing the strange black lines (horizontal and vertical) when browsing Time Machine though, hopefully that will be addressed in the next update.

Since the latest update I haven't noticed the artefacts when shutting down.

But a new problem has arisen. When booting up lines invariably flash on the screen, just beside the Apple logo.

I have restarted 2x since the 10.12.2 update. 1st time no artifact! Just restarted now & Yes still have screen artifact!

I did have a different artifact, mostly black screen, with fewer horizontal colored lines. Mostly near the top of the screen.

So, not fixed by the update. 😟

I d

10.12.3 beta is no better either. I'm pretty sure this bug is not on Apple's radar to fix at all. Oh well. At least it only happens on shut down or restart. I just wish I knew what was causing it.

Yes. Exactly the same, i.e., just after upgrading my iMac to Version 10.12.2.