Monitors swap content during sleep

[bkshepard]

I have two LG Thunderbolt 4k monitors connected to a Mac Mini (2018) running OS 10.15.7. If I leave windows open on my computer and it goes to sleep, when I wake the computer back up, the content of the two monitors has swapped sides. In other words, what was on the right monitor is now on the left and vice versa. My left monitor is the main monitor with the menu bar and they are not set for mirroring. When the monitors wake up, the left one is still the main monitor, but the content has swapped sides. Has anyone else experienced this? If so, were you able to solve it? I generally do my main DP editing on the left monitor and use the right one for various sub windows and plugin windows. Having to switch them back each time is a pain. BTW, I have tried swapping the cables and ports on the Mac, but it didn't make a difference.

[mikehalloran]

??? I run two monitors off my iMac Pro and do not have this issue.

How are they hooked up? Daisy chained or each into a USB-C port?

I didn't know that LG made 4K TB monitors. What model exactly?

[bkshepard]

They're both hooked up to Thunderbolt ports on the Mac Mini.

[mikehalloran]

A Mini only has one TB bus.

I didn't know that LG made 4K TB monitors or are they the 21.5" version. What model exactly?

[bkshepard]

LG 27UK850-W It's a 27". I guess it's actually USB-C, but the System Report says it's connected to the Thunderbolt/Display port.

From the System Report for Graphics/Displays:
Intel UHD Graphics 630:

Chipset Model: Intel UHD Graphics 630
Type: GPU
Bus: Built-In
VRAM (Dynamic, Max): 1536 MB
Vendor: Intel
Device ID: 0x3e9b
Revision ID: 0x0000
Metal: Supported, feature set macOS GPUFamily2 v1
Displays:
LG HDR 4K:
Resolution: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)
UI Looks like: 1920 x 1080 @ 60 Hz
Framebuffer Depth: 30-Bit Color (ARGB2101010)
Main Display: Yes
Mirror: Off
Online: Yes
Rotation: Supported
Automatically Adjust Brightness: No
Connection Type: Thunderbolt/DisplayPort
LG HDR 4K:
Resolution: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)
UI Looks like: 1920 x 1080 @ 60 Hz
Framebuffer Depth: 30-Bit Color (ARGB2101010)
Mirror: Off
Online: Yes
Rotation: Supported
Automatically Adjust Brightness: No
Connection Type: Thunderbolt/DisplayPort

[mikehalloran]

Your Mini has an HDMI 2.0 port. If your monitor didn't come with a cable, order up one from Amazon so you can return it if you must.

Otherwise, you might want to talk to Apple about this. They can go through your settings with you. Anything considered a MacOS issue gets free tech support as long as Mojave or later.

Something else to try is resetting the Launch Services to default. Not unusual for these to become corrupted after a Security update. Copy and paste:

Reset Launch Services

1. Open Terminal and run these commands:
2. sudo /System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -seed -lint -r -f -v -dump -domain local -domain system -domain user -domain network
3. (enter Admin password when prompted)
4. killall Dock
5. sudo mdutil -E /
6. Restart your Mac

[bkshepard]

Thanks, Mike! I always appreciate your advice. I'll give both a shot and see what happens.

[HCMarkus]

Option #2: Disable Sleep.

[mikehalloran]

Sure, no problem.

Something just occurred to me: I have mine plugged into ports 1 & 4 — how about you? If they are plugged into adjacent ports, that could be your problem. It can make a difference and Apple does have support docs on this.

I originally bought a pair of those for my iMP but those wide curved bases were too large for placing on each side and angling. I found a slightly different model with a compact, rectangular base that ;let both fit my desk. The only real difference is that yours has a USB-C input and can pass 60W charging downstream if connected to a TB3 Mac.

[url]file:///Users/mikehalloran/Downloads/27UK850_27BK85U_ENG.pdf[/url]

If the iMP had an HDMI port, I would have taken advantage of that to free up one of my USB-C ports.

[bkshepard]

Something else to try is resetting the Launch Services to default. Not unusual for these to become corrupted after a Security update. Copy and paste:

Reset Launch Services

1. Open Terminal and run these commands:
2. sudo /System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -seed -lint -r -f -v -dump -domain local -domain system -domain user -domain network
3. (enter Admin password when prompted)
4. killall Dock
5. sudo mdutil -E /
6. Restart your Mac

I just wanted to report that the terminal commands you recommended seemed to do the trick. So far, so good. Thanks, Mike!

[mikehalloran]

Something else to try is resetting the Launch Services to default. Not unusual for these to become corrupted after a Security update. Copy and paste:

Reset Launch Services

1. Open Terminal and run these commands:
2. sudo /System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -seed -lint -r -f -v -dump -domain local -domain system -domain user -domain network
3. (enter Admin password when prompted)
4. killall Dock
5. sudo mdutil -E /
6. Restart your Mac

I just wanted to report that the terminal commands you recommended seemed to do the trick. So far, so good. Thanks, Mike!

Ha!

Don't know why I thought to try that but it fixes a surprising number of issues. I first discovered it when none of the Macs in my house would shut down after they all aborted the March 2018 Security update. Last year, after the March 2020 update, my iMP had crashing issues and took 6 minutes to boot. Apple helped me find and remove the offending .kxt files but was stumped about the 6 min. boot time. I figured, couldn't hurt and bingo! I was back.

I also noticed that DP and Office booted a lot faster — then I recalled that the Terminal Command had flashed a page for every app and realized that it wasn't just resetting the system. Now, if an update or new plug causes DP to launch slowly, Reset Launch Services is a no-brainer.