Mac mini M2 + LG Ultrafine 4k issue

[pcd213]

The second monitor in my dual monitor setup (2 LG UltraFine 4k's) is flickering, and this only started a few days after downloading Sonoma. Both monitors are individually plugged into a M2 Mac mini. I'm not daisy chaining here. No changes to power supply. Does anyone know what's occurring here?

(1) When the flickering happens on the 2nd screen, the open window/program on the first screen sort of quickly zoom in and out.
(2) As the flickering happens on the 2nd screen, and I have a window in my first screen that I'm typing on (as I'm doing right now), the text that I'm typing will have a visible delay in appearing on the first screen even though the first screen remains lit.
(3) When I have the Displays setting window opened on the 1st screen, and the flickering happens on the 2nd screen, I always see both monitors appearing in the Display settings. The second monitor doesn't disappear from the settings pane when it flickers.
(4) I have a Magsafe charger plugged into the 2nd screen with AirPods Pro sitting on it, and when the second screen flickers, I do not see the AirPods Pro stoping and starting charging.
(5) The issue appears to happen more frequently as I'm typing or scrolling or doing something on the computer.

Here's a video of what's happening:
https://share.icloud.com/photos/0f9EZMVfnGXjSghhDeWi2JhYw

Setup:
- Two LG Ultrafine 4k monitors (24MD4KL)
- 2023 Mac mini M2, 8gb

I've been A/B testing a lot to see what could be the issue. I think my next test is to replace the thunderbolt cable and see if a faulty thunderbolt cable could be the issue here.

 

[Fishrrman]

There are numerous threads here at macrumors re the monitor "flickering" with m-series Macs.

You have a lot of reading and work ahead of you.

Seems to be related to the display not "synching" properly with the Mac's output.
Also, make sure the display is set to rcv the signal as "RGB", and NOT as "YpBr" (or whatever that is).

Lots of settings to try.
You should start a written log of changes you make, so you don't go in circles.

A video that might be of interest (even though the display in question is a Dell):

 

[pcd213]

Re activating this thread with a separate issue, but it’s not a new issue. I’ve dealt with this one since the beginning. Asking the forum for help.

Literally every single time I wake my Mac mini 2 from sleep with my two ultrafine 4k monitors, I need to manually increase the brightness (often on one or sometimes both displays) because it’s dimmed. I have no setting on my Mac mini to dim brightness at sleep. The same dimmed brightness on monitor issue occurred when I was using a MacBook to connect. Nearly certain it’s a LG issue or at least in how the software is interacting with these monitors. I have ensured that the monitors are running the latest firmware. Am I the only one? Any thoughts for potential fixes, folks?

 

[Kenny99]

M1 Mini and a single LG 27UN850-W. Updated to OS 15 and experienced the same as you. Dim display and low res. Settings did little to correct. Changed USB-C to HDMI to Display Port No changes. Had to Factory restore monitor, re install Firmware, delete Monitor profile, etc. Finally got it back to an acceptable setting.
Now running 15.1 and display is the same.

 

[pcd213]

M1 Mini and a single LG 27UN850-W. Updated to OS 15 and experienced the same as you. Dim display and low res. Settings did little to correct. Changed USB-C to HDMI to Display Port No changes. Had to Factory restore monitor, re install Firmware, delete Monitor profile, etc. Finally got it back to an acceptable setting.
Now running 15.1 and display is the same.

Dare I ask, how do I restore the monitor, reinstall firmware, etc? Sounds complicated. Man, these monitors are so problematic.

 

[Kenny99]

Just do a search for your LG monitors Model number and add the firmware update to the search. Mine is
"LG 27UN850-W firmware update".

 

[specialstyle]

Re activating this thread with a separate issue, but it’s not a new issue. I’ve dealt with this one since the beginning. Asking the forum for help.

Literally every single time I wake my Mac mini 2 from sleep with my two ultrafine 4k monitors, I need to manually increase the brightness (often on one or sometimes both displays) because it’s dimmed. I have no setting on my Mac mini to dim brightness at sleep. The same dimmed brightness on monitor issue occurred when I was using a MacBook to connect. Nearly certain it’s a LG issue or at least in how the software is interacting with these monitors. I have ensured that the monitors are running the latest firmware. Am I the only one? Any thoughts for potential fixes, folks?

This sounds like a monitor issue more than anything... you can make sure automatic brightness is turned off (usually it's not even an option but with a fancy screen like that it might be). Sorry, that is very frustrating