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iMac 27" 5K Late 2015 screen artefacts on shutdown

Bit of an odd one - upgraded to Mac OS Sierra, all working fine. When I shut the iMac down, the whole screen displays weird artefacts - (graphics glitch?), then shuts down fine. So not causing a problem, per se, but wondered if anyone else has had this issue?

iMac (Retina 5K, 27-inch, Late 2015), macOS Sierra (10.12)

Posted on Sep 27, 2016 1:25 AM

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359 replies

Sep 28, 2017 2:51 AM in response to Michael Kouloumos

I agree.


How long ago was it when the only publishing software used was Quark, hugely expensive but a requirement, I can't remember the last time I had a quark file supplied or even heard the software mentioned.


I also recall reading the following:


"Among his last advice he had for me, and for all of you, was to never ask what he would do. 'Just do what’s right,' " Cook said.


The crazy thing is I adore these products; my iMac was built at the cost of over £3,000, and I must spend over 25% of my working time trying to work out what's wrong with it.


It's in warranty with Apple care + but the manufacturer won't replace it, they will have me take it to a repair centre for to weeks and then confirm its fine.


Just do what’s right.

Oct 2, 2017 2:40 PM in response to fliefhooghe

As we speak I'm trying to decide if I go back to Sierra or El-Captain, I know many say if you do it right and you know what you're doing it's fine.


I have had Macs for over 20 years and never had problems until my late 2015 iMac, for the last two years and months in AppleCare I still had issues, I upgraded to an i7 4Ghz fully loaded and had problems, although they had got better.


My hope was High Sierra which sounded like it was optimised for high-end machines with flash drives, would finally fix the niggles.


NO, a lot of the original Sierra things are back, including closing screen artefacts; my iMac is also generally much slower maybe 10-20%, my Etrecheck report used to be 1.28 to 1.32 now it's 1.50.


As I mentioned, I'm running a late 2015 i7 4Ghz, 32GB ram, flash drive etc. and I get spinning balls and screen freeze/lag with just email open, safari can freeze the screen for 10-20 seconds.


The latest version of InDesign is not listed as compatible yet ( I think) either way the screen can freeze, basically loads of problems and some of the old ones back.


I have seen others say it's your thought for upgrading and that it's fine elsewhere, I keep a clean, updated Mac, I didn't install a beta version, I got a notification for the App Store for an upgrade.


I have a fairly current high-end iMac that's brought to its knees over basic software and find I'm spent 25% of my working day working with problems, admittedly I can restart and clear the cache, but don't want to.


SORRY, I went completely off topic there.


To answer your question, I would say no 🙂

Oct 2, 2017 3:53 PM in response to fliefhooghe

No problems for me yet in High Sierra. The graphical issue in the Time Machine also appears fixed.

The artefact/shutdown issue has been resolved in my case since Sierra 10.12.4 in late March. I didn't realize others were still having this problem.


I have all done clean installs via USB. Not sure if this has made a difference. Both the installer and the migration assistant completely failed on me for High Sierra, so ended up without another option anyway.

Oct 13, 2017 9:00 AM in response to fliefhooghe

Update: All sorts of weird little problems since, but nothing graphics-related. I did another completely clean install on both my Macs (plus my family's), and everything now seems resolved.


It seems doing a completely clean install from USB, and NOT migrating anything over (manually copying my files and reinstalling programs instead of using Migration Assistant) has made everything run way smoother. It's a pain, but has been worth it.

Oct 6, 2016 11:53 PM in response to JPRB_Mac_User

I have the same iMac and the same problem after upgrading to Sierra. Green lines? (sometimes other colours) Its really quite jarring to see. Its almost as if the graphics card driver quits before the machine is finished shutting down.


Reinstalling from Safeboot and resetting the PRAM etc doesn't resolve the issue and in the end I just gave up and restored using Time Machine back to El Capitan.

Oct 18, 2016 9:31 AM in response to JPRB_Mac_User

I have exactly same problem in similar circumstances. Here is the video I captured during shutdown https://www.youtube.com/watch?v=YioedHXY6ic

I chatted with their support, they recommended SMC & NVRAM test which didn't resolve the issue. Then they asked me to try diagnostic which again didn't help. I'm still chatting with them right now. I hope this is soft issue and not a Graphics card failure.


If we think logically then it's certainly a firmware/OS issue.

iMac 27" 5K Late 2015 screen artefacts on shutdown

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