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

Nope, I spoke too soon. The problem still persists even on static images.

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 am experiencing this issue as well, but I think it's attributable to a malfunction of the display itself — an Apple 30" Cinema Display — and not any sort of glitch associated with the model of Mac I am using. (In fact, I am not even on an M1 Mac, nor do I have the latest version of macOS.)

The issue seems to be intermittent, typically being most prevalent when the display has yet to 'warm up.' Following that point, any and all artifacts on the display tend to gradually decrease in intensity, until they're entirely gone (or, at times, present, yet simply less noticeable than before). These "artifacts" present themselves as vertical lines of striking similarity to those that OP has displayed. And, at one point, when the display was suffering from a particularly bad episode, said pinstripes were overlaid by a gray/light-gray pattern. (Both such instances are pictured below. The first shows the typical occurrence of vertical lines, over a dark background; the second shows what occurred during a more intense episode.)

Perhaps it's a T-*** board failure, or LCD panel failure? I really hope someone knows, because it is a darn shame that such an otherwise beautiful display is acting up in this way. I understand that this may be separate from what others are experiencing, but I still thought I might as well contribute some info from my end.

I also forgot to mention, I have tested both monitors directly connected to the MacBook as well as running through my CalDigit TS3 Plus dock and the issue eventually happens either way. I have made sure my dock is running the latest firmware.

I'm having the same issues as well with my new MBP M1 with 16GB ram running MacOS 11.4. My monitor is a 32" Samsung Odyssey G7.

The issue is easily replicable when clicking "share" or "save" on a youtube video. The screen will flicker every time. Appears to happen when the content on screen is dark. Seems to happen less when using the light system theme. Also messing around with black levels, contrast and brightness of the external display will bring up the scanlines. Bummer these two very expensive pieces of tech don't play nice.

The cables you want for HDMI-only Monitors (higher resolutions than 720p TV sets) are marked as Certified with an anti-counterfeiting tag and are labeled:

"Premium High Speed HDMI cable" or that + "with Ethernet"  --OR--

"Ultra High Speed HDMI cable" or that + "48G"

Cables with No Certification tags are good for your standard TV set, and not much more.

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If at all possible, try to use DisplayPort family cabling, or its equivalent over thunderbolt or USB-C.

"The issue is easily replicable when clicking "share" or "save" on a youtube video. The screen will flicker every time."

For my setup I can't confirm that. I have not yet found a way to reproduce the flickering issue, for me it seems to happen randomly.

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.

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.

That is pretty much exactly what I am seeing. And i do think you are correct, it is something about the monitor with what I assumed was the new graphics chipset on the M1. From reading reports, the issue seems to happen on only certain monitors but on a large scale. Like certain Dell monitors seem to have issues across the board. Both my Dell and my Alienware experience the issue when hooked up to my M1 but they work fine when used with my older Intel based Macbook Pro. I think something about the new Mac graphics chipset triggers something or corrupts a part of the monitor signal because once the problem occurs for me, the lines will often stay on the monitor even after I unplug my displayport or HDMI cable or after power cycling. The only thing that seems to help is messing with the refresh rate to make the lines go away or unplugging everything from the monitor and letting it run its LCD conditioning function for a couple minutes. It's really a crazy problem and I can't believe there hasn't been some kind of official response about it. Even if Apple were to release a list of possible monitors that are known to be problematic. I mean, I'm at the point where I just don't hook an external monitor up to my Mac and I have just been using my old one for work stuff.

<< once the problem occurs for me, the lines will often stay on the monitor even after I unplug my displayport or HDMI cable or after power cycling. >>

Then it is a display problem, NOT a computer or interface problem.

Grant is correct: this is a hardware issue pertaining to the display itself. On my display, the issue is intermittent; the lines usually appear when I first wake my computer up, and then they gradually either fade or just disappear altogether. They seem to vary in intensity — occasionally, being so severely apparent that they're an utter distraction for me.

All you and I need is for someone familiar with displays to identify the potential cause. From what I know, it could be either the T-*** board or the LCD panel. (It could even be the cables themselves, which lead to the T-*** board.) I'm getting close to just biting the bullet and ordering a replacement T-*** board for my Apple Cinema Display 30", since a used one is only $15-25. However, if a replacement board has no effect, I'll be sorely disappointed by the wasted effort. I'd cut my losses now, but I just otherwise love this display.

I have just got my Dell 34'' curved monitor today and I found this fixes it, but only temporarily.

System Preferences --> Displays --> Have the settings that you want for your external monitor, then go to Arrangement tab --> Check if the Mirror Displays box is ticked or unticked. For me I want this box to be unticked so if it's 1) ticked, I will untick, tick and then untick again 2) unticked, i will tick and untick.

I found this helps with this problem, but it is very inconvenient because I lock my screen every time when I go to toilet or do something or leave my table and every time when I lock back in, the problem will always come back and I need to repeat those steps every time. I am not very good at tech so please either Dell or Apple, fixes this.

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.