Faint vertical lines/static on external display connected to M1 MacBook Pro

PS: mine is 2017 Macbook Pro and not M1

did you successfully return this mac because of this issue (within the apple care warranty)?

I have the same issue with my M1 MacBook Air (16 GB RAM & 256 GB SSD). I connect my external display (BenQ GW2480T) Caldigit USB-C Pro Dock via Ugreen DisplayPort cable. The issue only appears on the darker areas. The last update of MacOS (11.5.2) also didn't fix the problem.

Just to be clear, I also have the same issue if I plug my monitor directly into the laptop so it most likely does not have anything to do with the Caldigit dock.

FWIW, hacking the M1 to output in RGB mode on the monitor didn't seem to help with the problem for me. I did think it was weird it was using YPbPr by default though. Using the HDMI to type c adapter from Apple didn't make a difference either. I also tried using a DisplayPort to DisplayPort cable and that also had the same issue. The only thing that seems to help it for me (and this just makes it happen less, not stopping it all together) is to set my monitors refresh rate to 240hz. At 59/60hz, the monitor not only has the vertical lines immediately, the monitor is also flickering or flashing. At 120hz and 144hz, the lines aren't immediately there but show up within minutes of using the external monitor. At 240hz, I can go a whole day without seeing them but they will eventually start up and I have to shut the laptop down, unplug the monitor, and then re-hook everything back up.

I really wish Apple would acknowledge this issue. It's really frustrating when they just pretend like nothing is wrong. You can search external monitor issues on the M1 in Google and find tons of examples of this and other problems. When I called support they claimed nobody else had reported anything like this in their system.

I want to know if anyone has resolved this problem.

1. Have you returned your unit yet because of this issue?
2. And, did Apple give you a better working MacBook?

Thanks, I hope someone can fill us in on their experience with this, that has resolved it in any way.

I'm running a Samsung Odyssey G7 and we just got a new firmware update that seemed to have minimized the effect but has not gotten rid of it completely, unfortunately.

Found these webpages via reddit that can replicate the scanlines and flickering (for me at least):

• https://i.imgur.com/noCE2tY.png
• https://ksr-ugc.imgix.net/assets/029/605/180/2c8ef349a4e074a44e2b472a811a403d_original.gif?ixlib=rb-2.1.0&w=680&fit=max&v=1593159119&auto=format&gif-q=50&q=92&s=0d153a1f5b7af1a570f2128d92a0a508
• https://www.hardwareluxx.de/community/attachments/whatsapp-image-2020-10-15-at-22-43-50-1-jpg.567680/
• https://rog.asus.com/wallpapers/

Here's a link to the reddit thread if anyone's interested: https://www.reddit.com/r/Monitors/comments/owzmdy/samsung_odyssey_g7_new_firmware_ver_10110_anyone/

I don't believe there is any solution yet and it totally ***** that Apple has not acknowledged this issue.

My high end laptop doesn't work with my high end monitor lol

I did speak to Apple within my initial purchase window and they said I could return the laptop if i wanted to but they claimed to not be aware of any issues with external monitors that were caused by the new M1 models. I chose not to return mine as it was also happening to the two other people I knew with new M1 laptops and of course, my same monitors worked fine with my old i7 Macbook Pro. So I assumed there would be a fix and another M1 would not solve the issue. The only thing I considered was exchanging for one of the Intel models but that would have negated the purpose of why I got this new laptop- to have the M1 and the better graphics performance.

I experienced this issue with a new M1 MacBook Air and resolved it for the time being by calibrating the white point and switching the "Resolution" from "Scaled" to "Default for display" though I'll be following this thread in case the issue recurs.