iMac 27" 5K Late 2015 screen artefacts on shutdown

I updated to the latest beta 2 and it hasn't glitched yet, but that doesn't mean anything aside from the hope that most other betas and releases have glitched on shutdown as soon as the update was installed. Wishful thinking I know, but I'll see. Sooner or later I'm hoping this gets a fix.

Has anyone tried increasing cursor size ?

did this a few days ago and not had any problems with screen at shutdown since might just be coincidence but worth trying

increase cursor size slightly in

System Preferences- Accessibility -Display

Cursor size change makes no difference. I use a slightly larger cursor - stops it from disappearing.

Recently I've had just a couple of shutdown artifacts, but the latest was more interesting - not stripes, but a page repeated across the screen - couldn't say exactly which, it went so fast, but it looked rather like a mail message.

The other case was not a full screen image, but a tiny one in the bottom right-hand corner of the screen.

Ok so. Just an update on this.

I logged this about a month ago. They came back and closed it due to it being a duplicate of another bug which I could see was open. Since they at least link the original bug number and status to your closed bug report.

I went in now and can see the original bug is closed. So I assume with the latest beta last night. Beta 3. This bug is now resolved? Can anyone confirm.

I don't have the iMac anymore.

I had this same issue recently. I have also seen issues when entering into Time Machine where there are strange artifact lines at the edges of the Time Machine Finder window that run the entire screen both vertically and horizontally.

Neither of these things seem to be causing any specific issue but my mac is not that old and it's worrisome.

Yep spoke to soon and it's back again! It looked like the iMac had gone to sleep but there was a thin multicoloured line at the top of the screen, the rest of the screen was black. Just shutdown and the entire screen was filled.

I just got a replacement for my iMac 27" 5k late 2015 with Sierra OS and after 2 days am starting to have this problem again. I am new at this and have no clue as to why. The computer works ok otherwise. Back to the PC world?

I have the exact same problem. It showed up when I first got the iMac (iMac retina 5k late 2015 model, 3.2GHz Intel Core i5, AMD Radeon M380, 1tb Fusion Drive) which scared me because that's what killed my old iMac. Stopped for a few months and is showing up again. Wonder if there's anything to do with the USB port...Because the blue lines came back after I attached an external HD for my time machine.

My old iMac died after the screen did the same thing. It's very scary seeing those lines. Anyone has any updates on it?

Thought I'd give OS Sierra a go again today as El Capitan had been giving me a bunch of issues of late (randomly freezing and crashing). The problem reappeared instantly in a completely fresh/clean install of OS Sierra. No external monitors connected or anything.

A few-month-old Mac (Retina 5K, 27-inch, Late 2015). Sierra 10.12.3.

I already returned my iMac once, when first purchased, due to this issue. The new (current) iMac has had the same problem. Waiting for fix like everyone else. I'm going to live with the issue for now, I guess. I'm done with downgrading back to El Capitan.

I have and after a bunch of hoop jumping Apple replaced my iMac because it was still under service and they could not fix the issue. From what I have seen it is a problem with these 2015 iMacs. This new one has had the issue once but it was restricted to the lower right of the screen not like the old one that had the entire screen full of the horizontal blue and green lines. No one I know can figure out why this happens. For me it was once in a while but my old iMac also had other issues.

It never occurred under El Capitan, only Sierra, so I would think its not the iMac as this would be a much bigger issue, its a driver/kext issue I would imagine introduced with Sierra. Also I think some people are mixing up the shut down issue with actual hardware problems by the looks of some of the posts.

I'm seeing it intermittently (cyan/magenta scramble on the screen) on shutdown, but in the following sequence: (1) screen goes dark (not black), indicating that it is still getting power, (2) the scramble, (3) screen goes back to dark, (4) after another second or so, the screen goes completely black, indicating that it is no longer getting power. Don't know if this helps anyone figure out the problem, but the glitching seems to happen well before the computer finally shuts down.

Here's hoping Apple comes up with a software or firmware fix for the problem.

I sent the fourth iMac 27 "late 2015 and this the 20 early days I worked well.

And now back to appear the stripes to the turn off it.

Is frustrating as have past the days of a return u now it would have that repair.

I don't think I do that four iMacs this defective must be otherwise.

What occurs that does not enjoy of my iMac why am pending of that leave them lines blue magenta etc in the screen.

:-(

I've sent my iMac to the service center 4 times (it's an iMac Retina 5k, 27inch,late 2015). It still have the multi colored artefacts during shutdown after collecting it from the service center for the 3rd time. The 4th time i went there, I told the service center to do a downgrade to El Capitan since I suspect it might be the OS issue and the service center did a full MRI and nothing is wrong with the hardware. In less than a day since i did the downgrade my whole iMac hang while i was working on Adobe CC Illustrator. Now every time i turn on my iMac and log in, it will hang at the desktop and then restart.

I've called AppleCare requesting for a refund. As this issue has really stressed me out since last year October, and my work production has been delayed (I had to make a total of 16 trips to the service center and it's really far away from where I live. Carrying a 27inch iMac is no joke, it's really heavy).

Took Apple about a week to get my reply on the refund and their answer was to simply replace my iMac and if it's defected they will repair it. That's it. Seriously...how is this any different from what i already went through?? I'm really angry and frustrated as an Apple customer this is really a HUGE disappointment. Tomorrow they will be calling me back again to get my answer on whether or not they will be replacing my iMac with a "brand new one". It's not like I have a choice in this issue.

Replacement with the same thing seems to be how Apple operated having a similar issue and "resolution". None of the diagnostic tools find any issues yet the problem persists. I have been watching this forum for some time and it appears that we are not alone in dealing with this issue and while it took Apple over a year to replace my computer the replacement has some of the same issues just not as often. Because Apple can't or won't fix the issue it would appear that while they have my money for this computer the words "return to PC's" comes to mind as I surely don't want to spend more of my hard earned money on a system or company that doesn't stand behind a defective product. I say defective product as my son has several older Apple products and none of them has the issues this one has. Good luck, I thing a lot of us could use some.