iMac 27" 5K Late 2015 screen artefacts on shutdown

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.

Hopefully it will solve it, but I don't have high hopes.

In reply to denxsation, I too heard (also through Apple chat employees) that it's better to actually call Apple(care) and report this problem rather than to chat about it. They apparently have more permissions.

Me neither.. I've 6 days left to return my (second) iMac, but I'll wait till grdh20 post a new update.

@Neutie, that's correct. They won't give this problem a high priority if two or three people will report this. Because Apple will say it's a hardware problem instead of software. That's what the Apple's supervisor told me.

I have had mine for just over a year, although I took out and have Apple Care, I am really reluctant to phone them as it appears that no matter how many exchanges they do, with either the logic board, display, or entire unit, the problem will never be fixed. I really can't be dealing with the hassle of all of that.

I'm only going by what I have read of other people's experiences in this thread, and that's exactly what appears to be happeneing. It's an annoyance and a bit worrying to see the artefacts, but it does seem to be software related - it's not happening in El Capitan. So I'm happy (ish) to sit it out for the time being.

'Apple' has no alternative then shipping Sierra with this horrible looking bug.

Not mentioning this software bug is another matter - it's a matter of money of course - the least damaging for business on the short term .

Silent as usual - excellent I agree for introducing new products - but unacceptable behaviour for this ... it's a disgrace !

'Apple' has no alternative then shipping Sierra with this horrible looking bug.

Not mentioning this software bug is another matter - it's a matter of money of course - the least damaging for business on the short term .

Silent as usual - excellent I agree for introducing new products - but unacceptable behaviour for this ... it's a disgrace !

----- More ....

I , though , do not have see this bug often (see my earlier posts for details) . However this is not the only bug , and not one I really worry about (though I plan to contact Apple , referring to these posts , within 1 year after buying it) ... I do hate the occasional complete freezing of the system , a freezing that cannot be solved by 'hard quiting' aplications or finder , and requires a power off - potentially damaging the mac and external disks data . I cannot remember to have had such 'bombs' with previous operating systems for decades .. that is baffling me .

I posted my machine info earlier here .. don't have it at hand now (on my ipad).

The problem is definetely related to Sierra , and not noticed by anyone with Capitan.

There have been similar weird screen artefacts reported with Sierra on the new laptops , but happening while using applications I believe I remember - and Apple has been trying to address that in the latest Sierra update.

Of course theoretically this 'event' could indeed be basically the results of a hardware issue and apparently 'caused' by Sierra only , if it is Sierra only that reveals an underlying 'hardware bug' somewhere ...