Flickering band of lines on my iMac screen since macOS Sequoia 15.6.1 update

Question

Flickering band of lines on my iMac screen since macOS Sequoia 15.6.1 update

Apple Imac M1 running Sequoia 15.6.1

This happened quite suddenly, just after a software update.

I have run diagnostics, but no error was found.

I have reloaded MAC OS from the Apple servers

I have checked all cables.

Pulled the power out for a few moments.

But nothing has solved it. Everything else is working just fine.

Is this a trip to the Apple store for repair, or is it terminal

Screenshot attached.

TIA

[Edited by Moderator]

Original Title: a flickering band of lines on my screen since update.

iMac 24″, macOS 15.6

Posted on Sep 10, 2025 5:58 AM

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Answer 1

rkaufmann87

Level 10

148,470 points

Sep 10, 2025 12:13 PM in response to suefromfareham

It is a well documented hardware problem, if you have AppleCare it’s covered otherwise it’s a repair (if you want it done) you will pay.

If You do not want to repair, some have gotten an external display and put that in front of the iMac.expect a repair estimate in the $600.00 range.

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Answer 2

a brody

Level 10

85,308 points

Sep 10, 2025 10:54 AM in response to suefromfareham

Flickering can frequently mean some issue with the video cable into the screen.

Notebook screens from Apple have been outfitted with a specific resistance when you push the screen back a certain amount. Don't attempt to push further back when you meet that resistance. A fall or drop can force a screen to go back further than it is designed to do, and start to pinch the cable to the screen. Newer OSes may have different tolerances for signal degradation.

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