Mac Mini (M1) Issues with Lg UHD Display (32UN500-W)

[crospa91]

Hi Guys,
Couple of weeks ago I've received my brand new Mac mini with M1 Chip.
Today I've received my new display, a UHD monitor 4K from Lg (32UN500-W) and this is when the trouble begin.

I can get full resolution and scaling without issue from the Mac mini, but when the display present darker colour (You can imagine the default big sur wallpaper at night of the monocular one with the shade of colour to very dark blue) the display start to flicker and display lines, small vertical lines all over the image.
The flash of these lines make me think to an issue with the refresh rate but I'm not too sure.

Funny enough if I restart the mini, the issue might not start immediately but as soon as I open an app, like maps or safari, or messages the flicker begins... so I don't really know what to do...

The weirdest thing is when I try to connect my MBP Pro 16" to the same display with the same USB-C - Display Port cable.. no issue at all. even in system report the MBP 16 can even see the serial number of the display when connected, things that the Mac mini can't.

Now I'm really confused and wondering if I need to replace the Mac mini, try with a different USB-C - Display Pot Cable (I read the the M1 is a bit fussy with these things) or it's simply a software issue and need to wait for apple to address it in a software update?

What you guys suggest?

I've attached a video of the issue happening here:

and these are pictures of the system reports where he monitor get identified in a different way between macs.

 

[Ultron]

Do you have HDR turned on in your monitor? I remember reading here that could make the colors look washed out or make the monitor unstable.

 

[crospa91]

Nope, the display don't have a specific setting to turn on HDR, but its the Mac that controls it and it's not on, even because otherwise the colours will appear all washed out, and it's impossible to look at it.
It's properly the display that don't get recognised correctly.

Following a suggestion from a guy on reddit, they suggested to reduce the refresh rate below 60Hz... I just now changed to 50Hz to see if it make a difference.

EDIT: No, no differences at all even with 50Hz

EDIT2: Connecting a HDFury Vertex between the Mac Mini and the Display I got this... and this surprise me!

Apparently the issue happen only when the display works in SDR, no issues at all in HDR but all the colours are washed out (The issue that goes over from Catalina)

But more interesting, the vertex reports that the signal coming from the mini is 4K30 422 BT2020 12b HDR 297Mhz 2.2T1 and the display accept exactly the same but it’s in 2.2 not 2.2T1.

Does anyone of you know what that T1 in the HDCP mean?

Pic of the vertex panel:

https://imgur.com/a/8JSrMlX

And if I turn on the HDR on the Mac Preferences the issue disappear but as you all know, all the colours are washed out very badly...

 

[vanlally]

Hi, im getting the same problem, I started to use the monitor in HDR mode, and I does flicker a small bit with that setting too, under certain conditions, im using HDMI, not sure if its the monitor though...

I got a bit of flickering with my MBP too, but not as much.

but in SDR, im getting flickering all over the place with my Mac mini, its nearly unusable,

 

[ECJ]

I just picked up the M1 Mac Mini and this monitor. It flickered only in launch pad once. After that, no flickering anywhere. I’m on Big Sur 11.1 Beta. With 2560x1440, connected through my Caldigit TS3 via DisplayPort 1.4 and HDR is off.

 

[murdink]

Hi there, were you able to find a fix for this ? Looks like people are also reporting it here https://forums.macrumors.com/threads/m1-air-ghosting-flickering-with-external-display.2271670/

 

[Robert Dada]

I recently purchased the Mac Mini M1 and the LG 5K Display (27MD5KL-B.AUSA) that Apple sells on their website and indicates it's compatible with the Mac Mini M1. For the most part everything works fine but occasionally when the screen saver kicks in and I enter my password to re-access the computer there is a visible glitch in the refreshed screen. It looks like part of the screen gets shifted down some pixels resulting in a screen with a " jagged" horizontal area going down the middle of the display. As soon as I reboot the system, everything is fine until the next time the screen saver kicks off the glitch. The display is currently connected directly to one of the two USB 4 ports. So far it's annoying but there's a "workaround". I'd prefer not having to reboot to clear the glitch though.

 

[aaronkagan]

FYI to all future users. I have my M1 Macbook Pro 14 inch connected to my 32UN500 via HDMI with no issues regarding flickering or scaling.