Mac Mini (M1) 2020, LG UHD monitor flickers on dark colours.

I have a Dell 27" S2721QS and am having the same flickering happening, I can't trigger it at will, but it's happening mainly when browsing websites with many pictures/autoplay videos. The effect takes up to 5 minutes to wear off after I close the app that triggers the flickering. I am not getting any definitive answers on whether or not this is a software or hardware issue and I don't wanna be stuck with a dud so will likely return the M1 Mac Mini since I'm still in the return window. I have tried different lengths/types of HDMI cables, nothing fixes it and I only have the problem with the Mac Mini, so it's either the HDMI port itself or the brains behind it. It's a shame that I have to return it for this as I was really liking the Mac.

Here's a little test I just did:

Create an image with a fill layer in Photoshop. Then play a little with the color picker, towards the dark grey end of the color space - I bet you'll find that some colors display flickering, some weird patterns or both.

Couldn't get any flicker with the BenQ monitor, but patterns in colors which should be solid.

I have this problem with my AOC 2879VF 4k monitor connected via Thunderbolt or HDMI. I replaced the cables with the Apple recommended, $expensive model and the problem persists. Apple replaced my Mac Mini M1 and the problem persists.

I also have an IIYAMAQ PL2390 connected to the same Mini and it has no issues.

Seems like Russian Roullette. I am tempted to replace the 4k monitor, but may end up with another one that isn't compatible.

Interesting to know that it occurs on multiple vendors' displays as I was thinking it was a problem with AOC, since they are cheap.

I have the 32'' UHD HDR Monitor with FreeSync monitor and using with the mac mini M1 and the problem is that the screen takes several minutes to go back on after sleep mode.. I tried other cable which I have and same issue. I changed the screen saver to "Never" and still slow to wake up after re boot or from safe mode.

When I first connected the monitor there was some flickering but after some hours of usage the flickering stopped. I sent a long time with Apple Care and she was very helpful to solve the problem but afterwards told me to wait for the report from diagnostic people and will get back to me in a few days.

So far this is the list of monitors reported with flickering Issues.

LG 32UN500 

Dell P27S21Q 

LG 27UL600-W Phillips PHL288B6

PHILIPS 328E

Dell S3221QS

LG 27GL650F-B 

ASUS MG28U 4K 

DELL U2421HE

DELL U2421HE.

Samsung U32R59

Dell S2817Q 

Dell U2718Q

LG 32UN650 4K

Dell U3818DW

Dell P2715Q. 

LG 24MK600M

Samsung LU28E590DS/ZA 28" 

Samsung R32R59x 

HP Pavilion 23xw 

LG 24MK600M

BenQ PD2700U

LG 29UB67

AOC 2879VF

PHILIPS 328E 

4k 32UL950-W.

LG 27GL650F-B

MSI MAG321CURV 4k

LG 24MP59G-P

Samsung LF24T350FHLXZX

ASUS PA248QV,

BenQ PD2700U

BenQ EL2870U

AOC Q2963P

JJC138,

I think you were right not to waste any money on Dell's adapters, I have the same monitor and the issue happens even over native HDMI so I don't see what a Dell USB-C adapter is going to do. I suspect Dell are confusing this particular flickering issue (the vertical lines in dark areas) with the full screen flickering/blanking, as they have a web page up for another monitor model with those adapters as the recommendation.

I've been able to replicate the vertical lines/dark areas flickering problem on my Macbook 2015 on both High Sierra and Big Sur, so this is either a long standing problem with MacOS or indeed the monitor just doesn't play nice with the Mac in general.

Bit disappointing as I've been a long time Windows user where generally you can plug in any old hardware and it works fine, for now my M1 Mini has been abandoned as I have no desire to spend any more time or money trying to resolve this, which is a shame as its a lovely little machine.

I posted in this thread earlier about having the issues with the HP Pavilion 23xw on my M1 MacBook Pro. I’ve since upgraded to the LG UN850-W 27” 4K monitor and have NOT had any flickering/vertical lines. In fact, as far as I can tell (and I am picky about these things), there are no graphical issues of any kind using this monitor. YMMV, but this appears to be one of the monitors that works with the M1.

I have the same issue with my M1 Mac Mini and my ASUS VP28U 4K display. In my case there is only this 1 display.

I tried it connected directly via HDMI (and yes with short/high quality cable) and I also tried it via OWC TB dock (via Mini Display Port to Display Port, and yes and yes with a short/high quality cable) and it occurs both ways.

The issue occurs for me most often after visiting "certain websites" (not all websites, but the ones that have the issue are repeatable). The flickering will occur and then it will slowly fade away and then it stops flickering.

By comparison, if I connect my 2018 Intel Mac Mini to all of the exact same hardware I mentioned above then there is no hint of flickering and everything works without issue.

I'm putting this ball in Apple's court and I think they need to take ownership of it. Its real Apple.

Just an update on my own issues (flickering lines on dark areas of display, display recognition troubles, etc):

the MLB of my mac mini m1 16GB has been replaced, and the problem is still persistent! the certified tech saw it with his own two eyes. so I guess there is really a fundamental issue with the 16GB RAM/8-core GPU variant of M1. Time for Apple to own this one. I am now demanding for a refund and NOT for aa replacement. I'll just buy something else.

Same problem here with a Dell 3221QS and Macbook Air M1 base model.

Managed to change the signal from YCrCb to RGB, which makes a slight improvement but it is still there. I've also found USB-C to HDMI works better than USB-C to DP, which would actually cause the screen to black out completely.

[Edited by Moderator]

MacBook Air M1 + Montery 12.0.1 + Zikko Thunderbolt4 cable M-TB4200 (2 Meter) + HYPERDRIVE GEN2 16-Port Docking Station + BenQ Manufacturer Thunderbolt3 cable (0.8 Meter)+ BenQ PD3220U

My new BenQ PD3220U has a similar problem of ghosting and flickering after a month of use. I contacted the BenQ manufacturer and learned that it was the cause of M1.

Yeahhh, no luck.

The last conversation I had with apple techs we tried wiping cashes in the two libraries listed in the photo below and rebooting for a moment everything was working great!! tho, a few moments later the caches refilled and the color flickering started again. If someone knows more about the inner workings of the libraries, there might be something worth exploring.

I Ended up caving and cashing in on my BestBuy protection plan. Traded in for a Samsung UR55 that (so far) has been perfect! highly recomended if youre looking for a color accurate 4k ips, not too pricy either.

Thanks for your advise !

My monitor was always flickering and ugly vertical lines appear especially when watching dark videos (on apple TV+, Netflix, Prime Video) ans also dark color websites.

I called AppleCare and we tried everything and even reinstalling( my current version is MacOs Monterey 12.2.1.

Now It worked for my 32UP50S LG 4K HDR monitor when I activated High Dynamic Range mode.

I also tried before with different HDMI cables, it was still flickering on my mac mini M1 2020.

I also tried with an Macbook air and my monitor works properly.

It is definitively a Mac mini problem and I don't know how to fix..

DP 1.1, Sharpness to 0, and very broad colour profile for monitor. If not all done then it is only near 100 % solution.

I have an ASUS MG28U 4K monitor. Thunderbolt to HDMI cable. Tried a different cable, as well as Thunderbolt to Displayport. Same issues. Interestingly enough I'm not getting that issue on my main display (Samsung U28E850) which is connected via the HDMI port on both ends. Perhaps it's a USB-C issue? Regardless, looks like we'll have to wait for Apple to drop a fix.