iMac 27" 5K Late 2015 screen artefacts on shutdown

I had the same problem, it seems to be a unique problem with sierra, it was bugging me so badly I just downgraded back to El Capitan and it's been fine since.

I performed the downgrade about 2 months ago and it hasn't come up with any weird artifacts or lines on the screen. Before the downgrade it did it about about 2 or 3 times a week. To me it also seemed that if the computer was doing some intense tasks such as video editing or gaming I would be able to guarantee that it would do it. https://youtu.be/hrfsnIOyVr0

It has been quite some time since you updated to OSX 10.12.04. At that time you reported that the update appeared to resolve the startup artifact problem.

Now that a lot of time has passed since your update, perhaps you would be so kind as to share your "current experience and opinion"? Has the update permanently resolved the problem.?

In advance, thank you so much for you input!

The new OS update seems to have resolved 97% of the artifact issues and I only experience a 1/2 wide black line that moves horizontally to fill the screen upon shut down once in a while. This is a good update as far as I can tell but it does not fix any issues with Garage Band.

Not odd at all. I have been following these posts for some time and recently posted the previous update to the Sierra OS seemed to correct the problem 97% of the time. However, to up date this information I recently updated to Sierra version 10.12.5 and the artifacts seem to have reappeared in a new way. Last time I shut down there was a clump of multi-colored artifacts in the top center of my screen. My iMac shut down ok and started up with no issues (I am currently using it) but sadly it seems that this new update "Un-fixed" part of the issue. Just as an FYI I had been surfing the Web prior to this latest incident.

For the most part yes it corrected the artifact issue but did nothing for garage band which still will not update or work correctly. While looking the web using Safari there are times when I get about half inch wide black lines moving horizontally from the top of my screen down to the bottom when I shut down. This is very intermittent and noted the the websites but upon returning to it the problem does not replicate 100% of the time. I have noticed that the fan comes on and is loud prior to my shutting down and getting the artifacts. Apple was kind enough to replace my first iMac as it had terrible issues. In comparison this one is much better but is still less than 100%. I wish I had better news but it is what it is and Apple products (at least this one) does not instill confidence in future sales of their products at least to me. Please note that I have family members with older Apple computers and they have no issues at all and find my issues strange to say the least. Good luck and I hope this post helps clarify what is happening from my seat.

Corrected typos below. Sorry for the double post and will check more closely next time.

For the most part yes, it corrected the artifact issue but did nothing for garage band which still will not update or work correctly. While looking at the web (using Safari) there are times when I get about one half inch wide black lines moving horizontally from the top of my screen down to the bottom when I shut down. This is very intermittent and noted the the websites but upon returning to them, the problem does not replicate 100% of the time.

I have noticed that the fan comes on and is loud prior to my shutting down and getting the noted artifacts. Apple was kind enough to replace my first iMac as it had terrible issues. In comparison this one is much better but is still less than 100%. I wish I had better news but it is what it is and Apple products (at least this one) does not instill confidence in future sales of their products. (At least to me.) Please note that I have family members with older Apple computers and they have no issues at all. They find my issues strange to say the least. Good luck and I hope this post helps clarify what is happening at least from my seat.

hmmm,... well I updated about 2 months ago to 10.12.4 and had no artifacts on shutdown since except today again... a rectancle about a firestick size quite in the middle of the screen with all kinds of colors... appeard for about 3 seconds on shutdown... so definitively not fully fixed this issue.

Will go on observing...

Dominik Gschwind

Mostly yes using the macOS Sierra version 10.12.5. I say mostly yes as there is still a rare occasion when the artifact issue still happens. Maybe 2 out of 100 shutdowns. Prior to this OS update the issue happen 50% to 60% of the time so, it is much, much better...at least on my computer.

oh, I can confirm the same artifacts issue Charlotte!

I updated to 10.12.5 four days ago and it suddenly happened again... but the last 2 days were fine.

it would really be appropriate that someone from Apple would comment the issue in this forum!

It would for example be a good feeling to get to know that the issues don't have any influence on the imac's lifetime...

Having installed the 10.12.6 masOS Sierra it appears that the issue may have been resolved. I update phew OS a few days ago so will give it a bit more time before I feel it has even cured. I will say that Apple is very slow to respond (if and when they choose to respond) so they may have lost a lot of repeat customers. It would also seem to me that Apple does nothing to have their apps fixed either so... go figure. I guess they have so much market share they don't have to worry about fixing things that have been broken for a long time. (2017 - 2015 = 2 years)

And the other day for the first time in a while, "THERE BACK!" This happened a couple of days ago on shut down only once but it happened again it was the black 1/2 inch wide black line going from top to bottom horizontally across the screen moving down in a cascading fashion. It doesn't seem to hut anything other than it is once again an annoyance. Come on Apple guys get this fixed before my extended warrantee expires. (glad I bought it? Is that the and? you were looking for?

I have exactly the same problem, same model iMac. I had it picked up under warranty and they changed the logic board but it still has the same problem. I'm hoping it's a software problem which will be fixed when Sierra is updated.

This seems to be an on going issue that was resolved for a while. I am again working with Apple to try and figure out why this is happening again. It has gotten better and for awhile was gone. However, my iMac has started doing it again and I also get the spinning beach ball occasionally. These two issues don't seem to be related and the beachh ball may be cause by an app that I down loaded from the App Store. Don't know yet.

The artifact issue on my computer does not seem to cause an issue in performance. Apple did replace my iMac once after trying to fix the first one but so far Apple has not been able to pin point the cause. My own theory is the issue is cause by click throughs when surfing the web but then I am a novice at the Mac world so?... ?

I fear upgrading to High Sierra since I had the same artefact issue with my 5k iMac late 2015. I am now running El Capitan and hoping High Sierra has resolved this. I miss upgrading without a care in the world Apple. Is getting bigger getting sloppier?

I was hoping for Apple to be an exception to the rule.

It is what helped elevate Apple that will bring it down, or at least it’s reputation in the short term. The closed ecosystem is what made this possible and it is it’s

instability now after all the tweaks that would allow it to be better for gaming, variety in hardware etc. Rushing not working perfectly, products in the market and then not fixing issues in the lifecycle of a OS is purely irresponsible. It was something Microsoft has done many times over the years. Just the other day IOS 11 removed the app switching functionality on all 3D touch iPhones, in an attempt to sell more iPhones 8 and X I assume. I did not miss not using the home button. In a graph with an upward tendency there is corrections downwards, and this applies to everything in life.

Let’s hope this is the case. Otherwise this is another example of a company growing big enough to afford deflecting from excellent customer experience to money making arrogance.

In the meantime I am sticking to El Capitan.