iMac 27" 5K Late 2015 screen artefacts on shutdown

Yes, clean install was a Sierra install. I'm on 10.12.1 right now.

I've got this issue as well.

https://youtu.be/A8laYDwAP4w

I sometimes even get a domino effect:

https://youtu.be/L04qK-PYE3s

I've the artifacts same as first video. Nothing the second.

I try a OSX 10.11 to external disk, I worked on it for two weeks, no artifacts on it.

I'll see if 10.12.2 resolve the problem, otherwise I downgrade as soon as possible.

I also get this strange colored horizontal lines artifact as I restart!

I really hope that Apple are aware of this and pursue a fix. I would just encourage everyone to log this on the feedback so they are aware.

Exact same here - 27" i7 32GB RAM 4GB M395X.

Only started happening after Sierra upgrade. Been on to support and done the SMC and NVRAM resets - no change.

They have advised me that it sounds like a hardware issue and to take my machine into an Apple store. However, from reading this thread it would seem unlikely to be a hardware issue - everyone is having the same problem, and only after upgrading to Sierra. I would be interested to know if anyone who did a clean install of Sierra is also having this issue - or is it just those who did the upgrade?

Clean install does not help. The issue doesn't appear on El Capitan. I'm on my 3rd brand new iMac 27" 5K 2TB machine and it continues. Ensure you have the issue elevated to Apple Engineering as its the only way it will be fixed.

Thanks for that - saved me the trouble of a clean install! Why have they replaced yours twice? Was it for this issue? How do I get it elevated to Apple Engineering?

First machine purchased through authorised Apple retailer. After going through the whole saga with Apple support I returned thinking it was a hardware problem with that machine. Second machine purchased from Apple retail shop - same problem - returned after 7 days. Third machine purchased from authorised Apple retailer with intention to use El Capitan. However I could not transfer my data from Time Machine or my old 2009 iMac because they were on Sierra. I had no choice but to upgrade the new machine to Sierra in order to transfer my data.

Keep telling Apple support of the problem - direct them here - and insist that it has to be elevated to Engineering. The Apple Store is not interested in fixing the problem as they cannot.

I bought two brand new 27" 5k, and as you have described, both have this issue. screen artefacts upon shutdown.

Same issue with my 2016 iMac 27" 5K Retina

Link to report problems to Apple?

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.