2020 iMac Screen Glitch on Shutdown

P3-Mac

I just purchased a 27” iMac 5K retina with the highest video card and I happened to have the same issue you are describing right out of the box. I actually have the same screen background.

Where you ever able to solve the problem. I’m considering returning my computer as I’ve only had it for less than a week. Any information you can provide I would greatly appreciate it.

FZ

StudioViv,

Thank you for the reply. I do appreciate you going through the details of what you have done in order to try and fix this problem. I was really hoping there was a fix to this especially since the computers are not cheap. I too hope it's just a software problem and not a hardware problem. I don't know if I could handle the same problem occurring when a new OS is released, or worse getting white strips across my screen like others on other forums have detailed. Apple should have addressed this already like you mentioned to give users an explanation and their plan moving forward.

Even though I already sold my previous iMac, I think I am going to return the computer and wait until this fall before school starts back up.

Thanks again,

FZ

@P3-Mac

Thanks for writing this down! Its EXACT the same issue I have. And exact this:

" But as soon as the Mac is working over say 15 mins, the glitch is evident on each subsequent shut down. "

I also tried everything possible to figure this out. I also have iMac 2020, 10-core 5700XT 16GB.

Apple could you response or solve this issue ? There seems to be an error on the high end of the iMac. We need a good working and solid shutdown, I can't wait for this shutdown stall every time, it just doesn't make sense.

I have actually rolled back to Catalina 10.15.7 where the shutdown glitch isn't replicated as it was annoying me no end and I won't update to Big Sur again until this, and other issues which are not being corrected are resolved (Bluetooth causing typing lag is another one that really needs looked at). Come on Apple at least acknowledge this Big Sur shut down issue is ACTUALLY an issue and what you intend to do about it....... PLEASE.

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.

Hey P3-Mac,

I hope this issue is software related. It's some trouble to pack everything and return this elegant beast and do a migration again.

It stuck me that this issue is so well described and still there is no answer from Apple. I can't fix this myself. Also the latest 11.3 MacOS didn't resolve this issue. I gonna call them this week and also direct them this forum. Maybe it will get some attention.

GusMcC, You'll have to let the rest of us know if you end up having the same issue. I ended up returning mine and repurchased one with the lower end graphics card. What a darn shame. I'll let everyone know if I experience the same issue with the lower end card. It comes in a couple days. As I mentioned in one of my earlier posts, I could make it occur anytime I let the screen go to sleep and then awaking the computer and then shutting down.

FZ

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.

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 agree on GusMcC response. Still... it might be a hardware thing which only appears on BigSur ofcourse... But as you say... i also roled back to Catalina and don't experience any issues which, to my believe, indeed shows it's the iOs.

Agreed, it COULD be a hardware issue but the fact there is different hardware involved across the Mac's (iMac, MacBooks etc.) that this is happening on, I still think this has to be software related. I still think it would be nice to get some clarity from Apple as their approach to this doesn't seem to be anything like as direct as it should be.

I also noticed my keyboard slip in my last message which might just a bit on the nose when I referred to Big Sur as "Bug Sur" ;-)

I did do an OS report about this issue but of course these reports don't generate a response.

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

Wauw FrankZ, let me reply on this that i have the 5500 XT card as well but i do have the issue as you can read in all my previous comments.

So, you now have a new computer and you don't experience the issue at shutdown? Now it is becoming really strange cause that would mean it might have something todo with faulty hardware.

And perhaps on the whole range of videocards used in iMacs.... as well as Macbooks... the AMD Radeons that is.....

In combination with Big Sur. Which could be a real possibility if Big Sur has a different usage of the videocard the Catalina has.

So it seems to appear on some of the videocards of some people so perhaps a whole line of Radeon cards just have this issue....

Which would mean if we would change the videocard the issue should be gone... is there someone who already has tried/done that with any feedback on this?