iMac 27 inch 2020 - Screen Glitch (Random Lines Appear on Screen)

I've just received my new iMac and noticed that from time to time a line glitch appears on my screen.

It's completely random, I thought it was related to intensive work/heat but sometimes even when the computer is idle I see the line on the screen.


It was really hard to capture it because it's so random, but I manage to record the moment a glitch happens. Unfortunately there's a lot of white background on it which makes it hard to see, but it goes across the entire screen https://www.youtube.com/watch?v=xw8Z4mVgYgE


The iMac is running fine, I ran all sorts of benchmarks for CPU/GPU and it's all OK, but from time to time I see this annoying line on my screen.


iMac Line (2012 and Later)

Posted on Aug 26, 2020 7:21 AM

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Question marked as Top-ranking reply

Posted on Nov 8, 2020 2:27 PM

Try the following: download and apply the macOS Catalina 10.15.7 Combo Update   


It fixes this issue:


• Addresses a graphic issue that may occur on iMac (Retina 5K, 27-inch, 2020) with Radeon Pro 5700 XT


249 replies

Jan 4, 2021 8:20 AM in response to Bunn_pt

my 2020 27" with 16GB has so many problems I dont know where to start. My old 2010 with just 1GB lasted 10 years without a single issue and was, imho faster than this POS.

  1. will not wake up after monitor sleeps, crashes and recovers only after holding down the power button for 5 seconds
  2. Memory hog on any video running in Safari causing a Safari crash and restart
  3. Blue-tooth latency and automatic typing of empty spaces at 30 to 40 key presses that cannot be backspaced
  4. Blue-tooth connectivity loss and recovered multiple times a day
  5. Since the introduction of B.S. a straight forward recovery from a Time Machine backup is no longer possible, you have to do a clean install and manually re-install every piece of software using the immigration assistance.

I have downgraded to High Sierra on a brand new iMac to resolve a majority of issues but of course I cannot update my Adobe or Apple products beyond that version as well


Apple went two steps backwards on this device if you ask me.

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iMac 27 inch 2020 - Screen Glitch (Random Lines Appear on Screen)

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