iMac 27" 5K Late 2015 screen artefacts on shutdown

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.

И у меня такая проблема

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.

Good video. I don't see how this can be anything other than an OS issue. I've never had anything even close to this issue on ElC. Did you also notice that the little spinning wheel (http://fs5.directupload.net/images/161018/z6ykon6w.png) doesn't seem to show up on shutdown like it used to on ElC?

My iMac 27" 5K Late 2015.

I have same problem after upgrading to Sierra, but don't anytime. ( 2 time/week)

😟

hope in the next update, probably on 27 October for new MacBookPro.

Support finally gave up, they didn't have any more tricks to try. They asked me to go to their store with this 10 kg of metal and check with geniuses. This is ridiculous. No way I'm going to do that unless it's a hardware failure which is not the case with this problem.

They asked me to raise this question to feedback team which I did. I request all of you guys to go to the following link and give them feedback. Unless they know this problem and acknowledge they are not going to fix it in next update.

http://www.apple.com/feedback/

Meanwhile I keep seeing some spectacular display of this weird graphic, I'll try to capture some more video.

This is random and doesn't happen always. It certainly doesn't happen when you use iMac for short time let's say 30 minutes or so and shut down. 3-5 hours of usage does show it more often. I'll say 90% of time.

As per my observation it happens when you keep iMac switched on for longer time let's say 2-3 hours. It doesn't show when you just use it for short duration - 30 minutes or 1 hour. Yes it's random and doesn't show all the time.

I found the same before downgrading. The buggy shutdown doesn't happen all the time but more often when the computer has been on for more than a few minutes.

I too have 5k 'screen knacker', booting in recovery mode, I ran disk-utility first aid as per usual on the mac's 2Tb fusion drive but for some reason it wouldn't begin the process, stating first aid failure every time. A new apple store has just opened near me, so bravo to broad st birmingham & incoming, we can at least agree the bull ring store round the corner is the worst but i have less far to lug this beautiful metallic angular malfunction, that weighs approx the same as a collapsed neutron star (heavy) - check out what ted landau say about his wife's iMac, avoiding iPhone 7 & apple watch because he is a grown up, even tho chuck booked him for that gig. Off-piste he's detailing some flaw in the fusion drive (mac store diagnostic) after taking the mac back & apple sorting it - heres the podcast - there's my warranty, best get a wiggle on

w.macvoices.com/rss/macvoicesvideorss

Have you or anyone found a solution for this problem yet? I cannot make a downgrade as I do not have a time machine backups, are you sure it's and iOS problem? my imac has just one month and I'm freaking out about this issue

Glad to see I'm not the only one!

I noticed this yesterday, it happened more than once but only when shutting down. I have run hardware diagnostics (on startup) and disk check for errors, all fine. Nothing appears to be running abnormally, it's just a horrible thing to see and gets you panicking a bit, it does need sorting.

I was doing some stuff in iMovie, and I thought it was something to do with that, but I did a restart after not using iMovie and it happened.

I have the same with my Mac Pro but at start up. Hardware checks have come back normal and without any issues. I suspect not might be a minor bug in the software. Saying that I haven't had any kernel graphic reboots for a while not like in the previous software.

I wouldn't let it concern you. As plxmas said. if its a problem downgrade back.

I have exactly the same problem with my late 2015 iMac 5K.

Same problem with me?

Shut down problem on IMAC