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

I have a related problem – every 30 seconds or so the entire screen or a part of it either flickers or is misplaced for a split second. It's hard to ignore it. I'm running MacBook Air M1, Big Sur 11.1, HP U28 4K monitor connected via Thunderbolt 3. Happens both at 30Hz and 60Hz settings.

The monitor is brand new, I'll ask a friend of mine to try with an Intel laptop to make sure it's not faulty though.

That does not sound good at all. I am itching to get the new M1 Mini, but I need two monitors. Currently have two Dell 27" premier monitors as I am a graphics designer and am used to working with InDesign on one and Photoshop on the other.

If the display problems don't get sorted quickly then I will just have to stick with my current setup and forget the Mi Mini.

I have switched my monitor from the LG 32UN500-W with LG 27UL550-W monitor and no longer getting the flickering issue. Im not sure if its because I switched from a VA to IPS panel monitor or that every monitor is different.

I have exactly the same problem, only I switched from the LG 27UL500-w IPS monitor to the DELL S3221QS with VA panel. For a long time I could not understand the reason for these vertical stripes. I changed a bunch of cables and realized that my MacBook Air M1 just doesn't work properly with monitors with VA panels, but I found that on/off NightShift helps for a while. Apple should fix this problem. I hope...

So, just a quick update... After installing the MacOS 11.2 update that was released today, the flickering display problem still occurs! It's very consistent when there is a scene that fades from light to black. Very disappointing...

Exactly the same problem here , Mac mini M1 , 8GB , 256GB , connected to a BENQ EL2870U, both HDMI and usb c to DisplayPort do this when the content on the screen is dark for example set Final Cut Pro full screen empty , it makes the picture shimmer/flash rapidly and produce lines down the screen , certain blue colours do it too. The second you switch to something else like a web browser window it becomes normal. Did you find a fix?

My guess is this is a GPU issue :-( running 11.2 here too

From reading the above the BenQ I have is a TN panel, it would appear the M1 chips like IPS panels?

The Dell S2817Q is an IPS display and has the issue on my M1 mini. I bit the bullet and ordered a display others have posted about using successfully with the M1 macs — the LG 27UK850-W — and it’s working via Thunderbolt and HDMI with no hiccups whatsoever. At least i know for sure that it’s monitor-to-monitor, not something about the particular Mini I received that chokes when ANY 4K display is attached.

Many Thanks, guess I will go for that display then! There is stock of the LG27UL850-W in the UK but not the LG27UK850-W which is discontinued , looking at the specs they appear to be the same though , might have to take a gamble on it!

I have this same issue on my HP E24 G4 IPS display with HDMI connection. I don't know when it get fixed. Flickering is happening throughout the four corner side ultimately. and sometimes it get extreme flickering. At the extreme moment I have to restart again to solve this. sometimes restart solve the flickering and sometimes it stays for a while and then calm down. but dark colors screen make it visible again and again. Please Apple fix this ASAP.

I was getting excited as after I installed the macOS 11.3 Beta I did not get the flickering at all and I got my hopes up that the issue was fixed.

However, yesterday after about a week of no flickering I got the dreaded vertical lines and then I got the strobing. Miserable.

usb c to DisplayPort made no difference for me however after having to still use the Ben Q monitor while working (which I am going to return) I was copying 6TB of data from one external usb 3 drive to 2 others backing it up , I bought a usb-c to usb a 4 port hub and another drive . During the backup which took several hours the display stopped the flickering and was perfect , having ejected the drives and put all cables back neatly the flickering is back . I have 2 ideas what it could be :

1) when usb is under heavy under load flickering stops and this is internal within the m1

2) connecting usb drive earths the Mac mini in some way to mains and causes flickering to stop. Will grab a multimeter and test continuity between usb shield metal , cases and earth.

i noticed that the flickering almost stop and doesnt happen much AFTER i stop using the build-in usb3 for attaching to any hard drives. i just use the USB-C connector and if i need to use USB 3, i'll use a USB-C to USB 3 hub and the flicker doesnt happen anymore, or less happening than before. im using the LG 32 550-w

From my tests with a multimeter just now I have one end directly connected to the earth in the mains socket (do not try this is you do not know what you are doing!) the other end probing the shield on the connectors on the back of the Mac mini. I notice that with the monitor unplugged via HDMI the Mac mini is 'floating ground' in other words resistance is very high between earth on the socket and earth on the shields of the USB cables still plugged in.

When I plug the monitors HDMI cable back in it grounds the whole of the Mac mini and resistance is low. This is because the monitor has a 3 pin mains cable with earth passing through to the HDMI sockets shield. It surprises me that apple does not ground the Mac mini directly this is the reason why when you touch MacBooks and run your finger across them you get a 'buzz' feeling as they are not grounded either. You and the MacBook have a potential difference to ground. Older MacBooks around 2011-13 came with a mains cable with the long cable attached to the brick which passed the earth ground through to the MacBook via the power brick. In the box there was also the small white adaptor that you could attach directly to the power brick shortening the overall length of cable , this thing didn't have a pass through ground. Crazy, in my studio this used to cause a slight hum which is how I found that out.

USB 3 devices can emit a lot of RF interference, grounding a cables shield which runs inside the length of the cable reduces RF so I think all these things are connected with the problem.

I have just updated to 11.2.1 so am going to wait until I see it happen again before I start disconnecting USB drives and like you say TechnicaStudios start using only the USB hub

Done some further testing and I am 100% sure its nothing to do with grounding, I removed all USB devices also disabled wifi & bluetooth, just had the Mac mini and screen connected up on a page I know to flicker like crazy. Nothing made a difference grounding the Mac mini and removing ground from the monitor didn't even make the picture change at all nor did adding and removing USB devices.

For me to fix it : adjusting the 'sharpness' on the monitors pictures settings from a default 5 to a 7 totally fixes the issue , again same webpage on the screen it changes from flickering with lines down the screen to perfect. The same also works if you adjust to a 3 but 7 gives more detail.

Something else that also works is changing from HDMI RGB PC Range from Auto Detect to 16 - 235 (full is 0-255) you don't want to do this though as it meant for using the monitor to watch films/DVD you loose grey levels.

There is def something wrong with the GPU in the M1 reacting with certain monitor settings, I also tried different refresh rates using switch res x and resolutions, nothing makes a difference.

The sharpness trick seems to have the most effect and fixes it .... will report back if it happens again with it on sharpness 7.

Just so everyone knows, this issue is NOT limited to the HDMI port on the Mac Mini... I've got a CalDigit TS3+ dock and the SAME issue occurs over the DisplayPort connection as well. It seems to be an issue with the GPU (M1 chip) or some sort of software/processing/filtering that's going on in MacOS.

Considering how widespread this issue is now, I'm shocked that Apple hasn't either released a fix or statement on the issue... I can't imagine there's too many people out there successfully editing/viewing video with a non-Apple 4K display on these machines, as they'd surely be experiencing this flickering / fine lines.