2020 iMac Screen Glitch on Shutdown

I agree. It due to the bug of OS.

I have a exactly same computer and was working perfectly fine with Catalina. Lot of issues came to me after updated to Big Sur. the splitter screen during shutting down..... the ventilation fan is constantly on disregard the room temperature is only 65 degree....put hard drive to sleep but external HDD is randomly on and off during the computer sleeping..... it's annoying.

update to 12.1.1 solve the my split screen problem.

Hi FrankZ,

I have tried a lot with my new machine and also was on the verge of bringing it back... but that would mean a great deal/hassle for me because we need it for work i couldnt easily miss it.

So 2 weeks ago i wiped whole system clean 2 times and did the following.

1. wiped clean > installed Catalina (no issues) > installed adobe stuff (no issues) > installed Bigsur <issue appeared>
2. wiped clean > installed Catalina (no issues) > installed Bigsur (issue appeared)

So, for me that meant that it has to do with Bigsur... so now i am running system in Catalina and keep a close look at system if the issue will appear after using imac for longer period of time (because it only happens if you use the imac for some time around 15 minutes or so).

But so far... all good...

I can't get my head around the fact that Apple is nowhere to be seen in this issue... that's what's makin me seriously doubt if it still isn't a hardware issue... It's like the don't want to address this issue maybe for being afraid they (again) have to do a call-back action on thousands of machines with this similar issue?!!! Just not responding to this makes me wonder about that. Instead of being open and honest about what this issue might be and that they are working on a solution in the background....

But okay, that's probarbly just me....

i will respond to any of the comments placed here. Greetings.

I have the same issue but it goes even further. It also appears on the log on screen or when switching to another user. Then it is also visible during working - and not only during shut down. Which is really annoying - especially if you spend a lot of money in order to have the highest spec iMac 2020 with top graphic card and max processor.

What I also noticed - and this is really seems to be a software issue then - is that while I have the split screen issue and I go into system preferences > screen > True Tone: When I uncheck True Tone the issue disappears, when I recheck True Tone the issue does not come back for some time until it eventually returns (I have not found the trigger). What I have not tried is to switch off True Tone with all users and if then the issue disappears completely.

It seems that my local Apple Premium Service Provider has solved the issue. I have my iMac back for two days and the issue has not come back.

In fact they replaced the Main Logicboard (3.6GHz 10-core i9, Radeon Pro 5700 XT, 1TB, 1GB Ethernet). The only downside is that I needed to migrate all data from backup since everything was erased (this was painless) and that I had no computer for 4 days ( a little bit more painful).

Should the issue reoccur I will let you know, but it looks good now for two days (Incl putting system to sleep, running system for hours and then logging out). I did not need to downgrade graphic card.

I find it hard to accept this is a hardware problem based on the numbers of us who are experiencing this issue on both iMac and MacBooks.

It would be unique in the extreme if this was a “universal hardware failure”. I rolled my OS back to Catalina and lo and behold, I can’t get this shut down glitch to occur on Catalina yet it does it all the time for me on shutdown on Bug Sur.

Would be nice to hear from Apple on this matter considering how widespread it appears to be.

I purchased a new iMac a month ago with the 10-core i9 processor, and the 5700 XT video card (although for my line of work, I really don't need it, but I figured why not). I kept seeing that glitch since day one. I then decided to see if others had the same issue and sure enough I found this thread, and the first posting (by P3-Mac) had an image of exactly what I saw on my screen every time I shut down. It's as though the picture was taken of my screen. Part of me was ****** because I dumped a bunch of money on the computer and this should not be happening, or at the very least Apple should address the issue. I was conflicted, do I keep it or return it.

What I found was, the only time I saw the glitch was when I let my computer go into sleep mode. No matter if I put it to sleep 1 minute after turning it on, I would see the glitch upon shutting down. If my computer never went into sleep mode, I never saw the glitch. These are just my observations.

I ended up returning the computer and bought the same exact computer except this time I ordered it with the 5500 XT video card. Yeah it sucked knowing I downgraded, but again for me it wasn't a bid deal. I told the thread I would get back once I got the new computer. I have not had or seen the glitch on my computer. I've been using it for a couple of weeks now and under many different conditions, I never have seen the glitch nor can I reproduce it.

I thought I would follow up.

FZ

This is what I think as well. As mentioned earlier in this thread. My local Apple Service Center has replaced my main board and thus Graphic Card 5700. My screen glitch has disappeared since then. So I assume it is a hardware issue which only becomes visible with Big Sur

So, i had the same issue. Contacted Apple, couldn't give me any proper answer to the issue and i have been told that they didn't know about it internally??? I also sended them the link of this discussion. So new computer, fresh out of the box, installed adobe pack and some standard stuff and i noticed the half screen issue at shutdown. It flickers 1 time, then shows half opaque exactly in the middle before actually shutting down.

So, my thougth where this. A: or it is a hardware videocard issue. B: it's iOs issue so software... my bet would be B because it is only happening at shutdown. A defect videocard would probarbly also show other issues during usage of the imac.

They couldn't give me a proper answer and told me to return the iMac... fine, it would be the second one i would be returning so i was not in a hurry to do so because i must de-install everything on it (again) and will cost me a lot of time.

But.... and here it comes.... i decided to wait for next iOs update... and today there was one... and to my surprise... the issue seems to be gone!!!

So, i am very curious if this is also the case with some of you guys? so please update and see if it is indeed fixed as it seems to be here. Big Sur 11.2.1

Hope to hear from somebody soon.

Agree on it most probably being a software issue and hardly a graphics card fault that only appears on shutdown. My 2020 iMac does split hue on shutdown too, my late 2015 iMac does not. Both are on 11.2.3. As long as I do not see this happening once during normal operation I will not bring my iMac anywhere. I would immediately notice a split hue while I'm working and since I got it in December 2020 and it has been running 8am to 6pm every weekday (at least) and some hours on the weekend I am pretty confident it is just a software issue during the shutdown process. FYI regarding hardware the iMac screen actually consists of two separate screens placed next to each other. So for sure an issue driving the two screens on shutdown. Fingers crossed it'll be fixed in one of the next updates.

I've just spoken with Apple support who are FULLY AWARE of this issue

which is currently being investigated from what I was told. I have also

been told it is a software issue and that a fix for this is likely in

in the next, or the next but one update. That's what I was told, so

I'm just feeding back. Very much worth keeping an eye on I would say.

So here is a picture of the glitch happening during normal operations. If you are using more than one user you will experience the same issue.

I am happy that I got my iMac repaired (replacement of Logic Board) - since then I have not experienced the issue anymore.

Hi, same here, reverted back to catalina... don't have that issue anymore. It has to be Bigsur bug.

You can also read other thread about this here: https://discussions.apple.com/thread/252114918

Pretty sure it’s not hardware related as previously mentioned. I can’t get this to replicate with the previous OS and apart from this glitch on shut-down with OS Big Sur, I have no other screen issues, again consistent with everyone else reporting this shut down Big Sur issue.

I rolled back a while ago now (Catalina) and have never had the shut down glitch occurring since doing that - comparing that with it doing it all the time under Big Sur.

I know it’s probably not the place for this, but the “other” Big Sur issues I had, most notably with lagging due to Bluetooth issues, ISN’T present under Catalina either ……..there are other things that bug me about Big Sur (I’m on a new 2020 iMac) but these are the two that forced me back to Catalina which is working perfectly. Simply has to be software related.