iMac 27" 5K Late 2015 screen artefacts on shutdown

@carol333 ...

Meanwhile, I also think that it's a software problem

Status Quo:

• I did let the i5 check in the store -- with all the stress testing and hardware testing -- no errors
• After I had got it back, and the artefacts did show up -- I replaced the new i5 with a new i5
• The new i5 also showed glitches!
• Now the i7 also showing the weird screen on shutdown - I don't know when I last did a shutdown, but I might have done a macOS update meanwhile

But a fact is: There are no so whatever issues working wit the i5, i7!

So these screen artefacts on shutdown are "only" something making me and apparently other people "nervous" ... rightly

Best,

TC

Apple - best Support ever (thumbs up) 🙂

Just got a call from AppleCare Help Desk to check what's going on and how to fix it.

To speed things up and you get a call as well.

• Make a screenshot of "About this Mac -> Monitor"
• Make a screenshot of "About this Mac -> Overview"
• Make a screenshot of "Monitor -> Color Profile"
• Open Terminal and run "sysdiagnose" --> keep that file for upload

Best,

Same problem here. See first three videos (also see comments): https://www.youtube.com/results?search_query=imac+2015+shutdown+distort

My iMac is at the repair center at the moment but I am starting to think it's due to OS Sierra. Hopefully Apple will sort it out soon. Anyway, if I get it back from the repair center with any news, I'll update here.

I have the same problem too. Bought my 27" iMac on the late of October 2016, OS Sierra. The shutdown issue started on the my first shutdown with my new iMac. From then on it has been occurring every 4/10 times I shutdown my iMac. Have sent back my iMac for repair twice and the problem still persist! Really hope they will come up a solution for this. Very frustrating.

Quick update about what most people already know: My iMac is currently being sent back from the Apple repair center with the message that it is indeed a bug in OS Sierra causing this glitch. No hardware problems. They are fowarding this to whoever is responsible for it. However, let's keep asking Apple to fix it.

Same here.

How many feel a hardware issue or software. I was told VRAM was not flushing cache prior to shutdown (geek friend). To repair the video card in the iMac, from what I am told is a skeletal repair. Had a friend with a total failue to the video card, and they now have flickers every so often all the time. Disheartening for such an expensive desktop.

Most definitely software/driver issue in my opinion. Given the issue is not present when rolling back to El Capitan, and that there are also strange lines appearing in the Time Machine window as reported elsewhere with Sierra.

I have exactly the same problem but I have found that shutting down automatically and letting the computer wait for the 60 seconds the problem does not appear. Would be interesting to see whether this is the same for all.

I have just received a new iMac 27" 5K Retina from Apple in replacement for a so called faulty model which also exhibits the same shutdown artefacts as the previous one did! Apple went to extraordinary lengths to try and fix the previous iMac. They replaced the LED screen twice! The main mother board twice! as well as both RAM chips and to no avail. That's when they decided to changeover the entire computer at no charge to me. The handling of this was impeccable and while I still have a (new) computer with exactly the same problem, I am pleased to know from this forum that apart from this quirky shutdown artefacts syndrome, the computer works beautifully!

How strange I thought that after getting away with it for a couple of weeks I had stumbled on the answer, however it is still working on my computer so who knows what the answer is perhaps the next update may help

I found a PATTERN.

First time I reported here about this weird psychedelic screen sometimes at shutdown was Nov 5.

Nov 27 I posted an update, with my machine data and reported that I start and shutdown daily my Mac , and the problem occured only occasionally.

Same is today , I think it did not return or only once .... but last week it occured with logging-out several times in a row - a new situation and a pattern ! Let me explain :

I always am the only user on my machine and only use 1 account. So normally I start the mac and login into my account , and at the end of the day , do a simple shutdown.

I do have several other accounts with apple-ids at my mac , but these are sleeping for many years - I do not use them.

However last week I needed a test using one of these sleeping accounts (because I wanted to test a dropbox link for downloading by others who do not have dropbox - but that is irrelevant here). So I logged into another account on my machine and updated that sleeping account (from the mobileme era) with a new password for the apple-id and installing icloud drive etc for that account.

For the tests I wanted I had to go from one to the other account and back several times. For that of course I did not shutdown the mac in between , but logged out and in the 2 accounts several times.

For I think 6 out of 7 consecutive times* I logged out of one of these accounts I got the full blown 'screen artefacts' - while shutting down once in between of these sessions did not result in the screen artifacts.

The next day I worked in my usual account , and now I had the screen artefacts' at shutdown ...

Because over the past months I have seen that only a few times - I thought that perhaps that other account on my machine (with an active icloud drive) - that I no longer needed really - may have an effect. So next decided to log out of icloud in that extra account (which deletes the icloud drive..). Now over the past days the screen artefacts did not return on shutdown.

Conclusion : complete shutdown is not needed for the problems to arise ... logging out ... or ? 'leaving' the icloud drive may suffice for the problems to arise , and like I posted last time , it is a software problem.

The problem with Apple probably is 'they' are focussing only on the functioning of the new laptops with the touch bar.

I firmly believe , it is also the changes in the Sierra OS needed /introduced for the new laptops with the 'graphics touch bar' that caused these 'graphics artefacs' on the iMac.

I am using the Mac some 30 years and never before had serious issues like now with this machine , first some months ago with El Capitan - with the 'bluetooth issue' at start up , with no connection of keyboard and mouse - and now again with Sierra and the graphics artefacts. However before El Capitan I always waited with upgrading the Operating System around at least a year after introduction after around the 5th minor update ... when all issues have been corrected.

With the latest 2 OS upgrades - Capitan/Siera - I was forced to upgrade much sooner because of the integration with iOS ... and important corrections such as for the Notes app .. Also upgrading iOS on iphone / ipad is forced upon you with hampering warnings... Besides upgrading for security is more relevant now...

Interesting is that these artifacts do not occur on my

iMac 5K 27'', Late 2015, i7 4Ghz, Radeon M395 (no issues)

on

iMac 5K 27'', Late 2015, i5 3,2 Ghz, Radeon M380

they occur on the shutdown.

The i5 has been even replaced by a new one and has now the same issues.

Very annoying and does not make me feel comfortable with this iMac.

And even if it works and has "only" these lines on the shutdown, it's like to say : Oh, your car drives well - it only makes a hop to the left when you stop your engine ... Would you trust that car ?

Thank you for confirming the situation with both i5 and i7. I have an i5 and do see the graphic artefacts on shutdown, but wasn't aware i7 might not be affected.

Hopefully Apple are fully aware now with more of us reporting this bug.

I spoke today with an Apple Care supervisor and she told me that this problem should be fixed in the latest update 10.12.2. or by reinstalling macOS Sierra. I reinstalled my brand new iMac but I've still the screen artifacts on shutdown. She'll report this problem to the engineers of Apple and comes back with an answer in a couple of days. I'm still doubting to return my brand new (second) iMac to the store.

Everyone who have the same problem should call Apple Care instead of filling in a feedback form..

It is a Sierra only issue. I'm on the latest beta chain so I'll post back if I see it again. As a matter of fact I think I saw it the first shutdown after installing the latest beta the other day already, but I'll watch for it again. I'm not sure the graphics update was for 2015 imacs anyway.