I just upgraded to Big Sur 11.4 from Catalina 10.15 on my MacBook Pro (16-inch, 2019). It completed without error.

Everything is fine, except...

Randomly, approx once per hour, but can be as little as a couple of minutes apart, the entire screen goes black for about 1/2 second, then it returns to normal.

This never happened before the upgrade.

Any ideas on how to stop this behaviour?

  • Try safe mode (hold shift at start till you see the Apple logo). SMC reset and PRAM/NVRAM resets might be worth a shot as they don't take much time and can't do any harm. Edit your question with the results from the suggestions. I have the same Mac and my upgrade went well. So maybe a search on the Apple forums for other people having similar issues. Jun 7, 2021 at 14:15
  • @SteveChambers thanks for the suggestions. I tried each one separately to scientifically determine what fixed it. Unfortunately none of your suggestions made any difference. Disabling True Tone did the trick (see answer).
    – Bohemian
    Jun 8, 2021 at 21:45
  • My issue was faulty HDMI cable, so you can change and try
    – Arefe
    Nov 11, 2021 at 2:53
  • @Arefe my problem was with the laptop’s screen. I don’t actually use a second screen.
    – Bohemian
    Nov 11, 2021 at 2:54

2 Answers 2


Disabling True Tone fixed the problem.

System Preferences > Display > Uncheck "True Tone"

FYI many posts/blogs/sites complain that true tone causes flickering.


I had the same problem running Monterey. The problem was that I had an HDMI cable plugged in. My iMac was changing resolutions. The solution was to unplug the cable.

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