Chosen Solution
I’ve done some research and it seems more people have the same issue. This video ain’t mine (so far my issue ain’t that bad only similar): https://www.youtube.com/watch?v=AWW9bt1T… It can go days with no issues and then it happens usually starts when I’m scrolling through my mails on Outlook and when it does start even checking my apps on the dock (Dock’s amplifier effect) triggers it as well. Then I reboot and all is well for days… What is that? Could it be faulty cable or a software issue maybe a firmware thing or even something with Mojave’s Metal…? Oh and I’ve seen the copy/paste reply sent to others online saying ‘replace display here’s the guide’. That’s not what I’m after. First those displays are almost as expensive as the iMac itself but also other than this random flickering it works fine there has to be an answer other than the usual Apple motto ‘pay heaps of cash to replace or a truckload of money to buy brand new’. This is iFixit, doesn’t anyone knows how to fix this…? Update (07/14/2019) After reading on MS forums many more people having issues with Outlook flickering screen on Mojave I downgraded mine to a previous version. Actually tried as far back as 2011 but that wouldn’t read my files and 2016 wouldn’t even run on Mojave (all other Office 2016 apps would though) so I reinstalled Office 2019 and left it un-updated. Current Outlook version is 16.19 will see if it still happens or not and keep this here updated. Also gonna do the ‘heat management’ thing mentioned below anyway. Just gonna take a bit longer so the ‘downgrading test’ still holds value I think… Update (10/04/2019) An update on the issue: running a slightly outdated version of Outlook seems to have ‘fixed’ it. Haven’t had ANY issues since so yeah it’s either an Outlook problem or dark mode compatibility (in my case dark mode vs Outlook). Either way it ain’t hardware which is good news :) What is not good news is the fact that the screen does have backlight bleeding which to be fair mine is hardly visible but once you see it you can’t unsee it. :(
Sadly you’re not going to like my answer either ;-{ Your display assembly has failed, you need a new display. OK I get it… What!! What could be going on to do this!! WHY, WHY!!! OK, heres the dope! Your display has a logic board on it which is called a T-CON it drives the LCD panel X & Y lines that energies the given pixels row by row, column by column! So when it messes up you get the fireworks you saw on in the video. Its also possible to damage it if you don’t use the proper tools taking the display off.
Review the iFixit teardown here iMac Intel 27" Retina 5K Display Teardown Jump down to Step 6 for more details
Mine does the same thing when I scroll through my Outlook. Reboot and it’s fine
This doesn’t look like a screen issue, we just had one of these Macs in with the same issue, changed the screen and the same problem. This looks like an outlook/dark mode issue
I have the same issue with my iMac when rendering or working using Final Cut Pro X. It happened twice already. I didn’t have this problem before updating to macOS Mojave 10.14.6. This is a bummer. iMac (Retina 5K, 27-inch, Late 2015) 3.3 GHz Intel Core i5 AMD Radeon R9 M395 2 GB I have already reported this problem to their e-mail feedback system and I haven’t got any reply yet. My suspect is this is a software problem (metal & gpu compatibility) as it behaves this way only when using certain apps especially those that use the GPU heavily or those that rely a lot on RAM. IDK
Ive got 20 of these 27” iMacs, each with a 27” secondary Apple display. Just about every single one has exhibited this problem. Reboot fixes it. Can start again in a day, week, or month, totally random. I certainly don’t think this is hardware related.
I see it’s been a while since this question was asked, but I thought I’d add my testing / solution. I have a spare 27” Apple Display that’s maybe 5-6 years old. I had read something on another blog to test the built-in monitor by attaching an external monitor to see if the flickering continued. When I attached the second monitor, it continued flickering. I went in to play with the monitor setting and when I changed the settings to “Mirror Display,” the flickering went away. As soon as I set the monitors to continuous, the flickering came back. It’s 100% repeatable (every time I set the monitors to mirror, the flickering goes away. I’m going to test it with a smaller monitor as soon as I get a Thunderbolt to DVI adapter. Good luck and hope this works for you.
