Monitor Randomly Disconnects

[oyasuna]

This is related to this thread, but I thought the tone of the message was inappropriate, so I've opened this thread.

We, the user base, definitely need a fix, but we need to be respectful of the engineers who have spend countless hours developing this wonderful software and hardware. Poor tone or unjustified claims of fault will not solve this problem.

I too experience the same issue.

Background:

I have a 2021 16" MacBook Pro. I have two monitors attached via a Plugable Docking Station. Oddly enough, only one of the monitors (2nd) is listed in the DisplayLink Manager tool window (VX3267U-4K).

On 5-22-25 at 12:13pm, I upgraded from macOS 14.7.2 to 15.5 (and am certain this is the exact time because I checked with $system_profiler SPInstallHistoryDataType | grep -A 4 "macOS"$. At the time, I was on DisplayLink Manager Graphics Connectivity 1.12.2.

Since then, I have uninstalled via Homebrew and installed version 1.12.4 from the DisplayLink website.

What I've tried:

1. Restarted my computer.
2. Uninstalled DisplayLink via the tool and reinstalled it.
3. Completely wiped and reinstalled macOS.

The issue persists.

I decided to observe the issue to attempt to find a pattern.

Observation:

1. ~20:26:45 - My 2nd monitor disconnected.
2. ~20:27:10 - I enabled my 2nd monitor.
3. ~20:33:25 - My 2nd monitor randomly disconnected.
4. ~20:34:07 - I enabled my 2nd monitor.
5. ~20:38:58 - My 2nd monitor disconnected.
6. ~20:39:15 - I enabled my 2nd monitor. I then stepped away from my computer.
7. ~21:05:50 - I returned to my computer. At some point, my 2nd monitor disconnected.
8. ~21:06:20 - I enabled my 2nd monitor.
9. ~21:10:36 - My 2nd monitor disconnected.
10. ~21:11:00 - I enabled my 2nd monitor.
11. ~21:11:12 - My 2nd monitor disconnected.
12. ~21:11:33 - I enabled my 2nd monitor.
13. ~21:18:53 - My 2nd monitor disconnected.
14. ~21:19:09 - I enabled my 2nd monitor.
15. ~21:25:13 - My 2nd monitor disconnected. Taking a break.
16. ~21:52:42 - I enabled my 2nd monitor.
17. ~21:54:30 - My 2nd monitor disconnected.
18. ~21:54:45 - I enabled my 2nd monitor.
19. ~21:55:15 - I watched a funny video on YouTube.
20. ~22:00:52 - My 2nd monitor disconnected.
21. ~22:04:02 - I enabled my 2nd monitor.
22. ~22:07:05 - My 2nd monitor disconnected.

During this observation, I also monitored the two DisplayLink processes' CPU and memory usage. I did this via $htop -p $(pgrep -d, -f "DisplayLink")$. When my 2nd monitor is connected, $DisplayLinkUserAgent$ uses ~152MB of memory and fluctuates between 0% and 5% CPU usage, and $DisplayLinkXpcService$ uses ~6400K of memory and stays around 0% CPU usage. When my 2nd monitor is disconnected, $DisplayLinkUserAgent$ uses ~151MB of memory and fluctuates between 0% and 1% CPU usage, and $DisplayLinkXpcService$ uses ~6400K of memory and stays around 0% CPU usage.

I also monitored $DisplayLinkUserAgent$'s file system activity. I did this via $sudo fs_usage -f pathname <pid>$. For the most part, it just accesses its log file stored in $/Users/<username>/Library/Group Containers/73YQY62QM3.com.displaylink.DisplayLinkShared/Library/Application Support/Logs/DisplayLink Manager.log$. It will access other things if you interact with the DisplayLink Manager tool window. Unfortunately, the log file isn't useful for users. Each log message is encrypted then base64 encoded. Not sure why this is necessary...? If someone knows, please let me know.

I also monitored the DisplayLink processes' network usage. I did this via $sudo lsof -i -r 1 | grep "DisplayLink"$. There was no network activity at all during this observation. (After the observation, I checked if DisplayLink Manager sends any network requests if I quit and restart it. It did not. Props to the developers for designing this to work completely offline.)

Random Notes:

1. I noticed that the CPU usage percent of DisplayLinkUserAgent spikes when you click on a window in a different monitor than the focused window, or drag a window to a different monitor. The developers could probably optimize behavior this by prefetching information based on the location of the mouse cursor.
2. Note to DisplayLink developers: I found your AES encryption/decryption function at 0x1000b0f5c and your AES key derivation function at 0x1003467d8. As far as I can tell, you derive the key from hardcoded constants, a seed, and a hash computation. You use a fixed seed in multiple places, which is definitely unsafe. I decided to stop here, but I doubt it'd be hard to decipher your key derivation algorithm and compute the key. To fix this, you should add some randomness and maybe add a derivation based on some unique system value.

Extra:

Output of $system_profiler SPDisplaysDataType$ (when all monitors are connected):

Graphics/Displays:

    Apple M1 Pro:

      Chipset Model: Apple M1 Pro
      Type: GPU
      Bus: Built-In
      Total Number of Cores: 16
      Vendor: Apple (0x106b)
      Metal Support: Metal 3
      Displays:
        LG HDR 4K:
          Resolution: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)
          UI Looks like: 3840 x 2160 @ 60.00Hz
          Main Display: Yes
          Mirror: Off
          Online: Yes
          Rotation: Supported
        Color LCD:
          Display Type: Built-in Liquid Retina XDR Display
          Resolution: 3456 x 2234 Retina
          Mirror: Off
          Online: Yes
          Automatically Adjust Brightness: No
          Connection Type: Internal
        VX3267U-4K:
          Resolution: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)
          UI Looks like: 3840 x 2160 @ 60.00Hz
          Mirror: Off
          Online: Yes
          Rotation: Supported

I noticed that the $DisplayLinkUserAgent$ binary contains both x86_64 and arm64 builds ($lipo -detailed_info /Applications/DisplayLink\ Manager.app/Contents/MacOS/DisplayLinkUserAgent$). Props to the developers for spending the time to do this.

Conclusion:

Based on the things I attempted to fix this, the observation, and this thread, I think the issue is macOS. At some point, a macOS update caused the issue.

Bottom line: Regardless of the source of the issue, it is a problem that needs to be fixed. We cannot expect Apple to fix it. Until a fix is applied from the DisplayLink developers, the products we've paid for are rendered useless.

[rboerner]

Originally Posted by oyasuna

I have a 2021 16" MacBook Pro. I have two monitors attached via a Plugable Docking Station. Oddly enough, only one of the monitors (2nd) is listed in the DisplayLink Manager tool window (VX3267U-4K).

The docking station you are using is a hybrid. The 'Display 1' video output group is driven by the video output capabilities of the host computer. It is not driven by DisplayLink technology. This is why only one display appears within the DisplayLink Manager Application status window. The 'Display 2' and 'Display 3' video output groups are driven by DisplayLink technology.

Originally Posted by oyasuna

Unfortunately, the log file isn't useful for users. Each log message is encrypted then base64 encoded. Not sure why this is necessary...? If someone knows, please let me know.

Synaptics (the creators of DisplayLink) encrypt the log files in order to protect their intellectual property.

Given you are using a Plugable brand docking station, if you have not done so already I would suggest contacting Plugable directly for assistance --> https://plugable.com/pages/support

If you wish to pursue the matter with Synaptics (DisplayLink) directly, then I would suggest you follow the procedure outlined here --> https://support.displaylink.com/know...to-displaylink

[oyasuna]

Originally Posted by rboerner

The docking station you are using is a hybrid. The 'Display 1' video output group is driven by the video output capabilities of the host computer. It is not driven by DisplayLink technology. This is why only one display appears within the DisplayLink Manager Application status window. The 'Display 2' and 'Display 3' video output groups are driven by DisplayLink technology.



Synaptics (the creators of DisplayLink) encrypt the log files in order to protect their intellectual property.

Given you are using a Plugable brand docking station, if you have not done so already I would suggest contacting Plugable directly for assistance --> https://plugable.com/pages/support

If you wish to pursue the matter with Synaptics (DisplayLink) directly, then I would suggest you follow the procedure outlined here --> https://support.displaylink.com/know...to-displaylink

Thanks for your quick response and the valuable insight.

I should mention that I have several coworkers that use different DisplayLink docking stations than me (some completely different brands), and they also experience the same issue. One of my coworkers is still on macOS 14 (he didn't upgrade when the rest of us did and noticed the issue with the DisplayLink drivers). This further demonstrates that this is most likely an issue with macOS. Regardless, this is something that Synaptics needs to fix.

Lots of people have already followed the support procedure (and so have I, patiently waiting for a response).

P.S., I only mention the stuff about the logs because I was curious. Completely makes sense to protect intellectual property! I also did some light reverse engineering out of curiosity, and did find a flaw in their encryption, which I pointed out in my original post. I hope this information is relayed to the developers.

[oyasuna]

Another relevant thread: https://displaylink.org/forum/showthread.php?t=69473

[marcus.thiel@gmx.de]

Originally Posted by oyasuna

Thanks for your quick response and the valuable insight.

Lots of people have already followed the support procedure (and so have I, patiently waiting for a response)

The point is that may people including me have now filled a lot of service support questions, and there is still zero response from Displaylink .... this is a very very bad. way to deal with customers, and it doesn't look like there is a fix.

[oyasuna]

Originally Posted by marcus.thiel@gmx.de

The point is that may people including me have now filled a lot of service support questions, and there is still zero response from Displaylink .... this is a very very bad. way to deal with customers, and it doesn't look like there is a fix.

The point of this thread is not to blame or shame, please. There is a reason they've not responded. DisplayLink is obviously a very important product, with an enormous customer-base. There are viable alternatives in the market, and Synaptics knows this, so it's not like they are intentionally ignoring customers. I'm sure the development team is freaking out trying very hard to fix the issue.

Also, remember that support data is ~50mb. While this may seem like a small number storage wise, from a technical perspective, it's a lot of data to shift through.

Patience and respect will win this.

[oyasuna]

Note that the issue is present in general: https://www.reddit.com/r/MacOS/comme...a_few_seconds/

https://answers.microsoft.com/en-us/...6-e20fe9dd0170

[Szymon]

Originally Posted by oyasuna

Note that the issue is present in general: https://www.reddit.com/r/MacOS/comme...a_few_seconds/

https://answers.microsoft.com/en-us/...6-e20fe9dd0170

Hi oyasuna,

These links relate to a well-documented issue with screen sharing during video calls.
Regarding your specific problem, I highly recommend contacting technical support, as previously suggested by rboerner. There is no known generic issue with macOS 15.x that would prevent DisplayLink from functioning, so your case needs to be analyzed individually.

Regards,
Szymon

[oyasuna]

Originally Posted by Szymon

Hi oyasuna,

These links relate to a well-documented issue with screen sharing during video calls.
Regarding your specific problem, I highly recommend contacting technical support, as previously suggested by rboerner. There is no known generic issue with macOS 15.x that would prevent DisplayLink from functioning, so your case needs to be analyzed individually.

Regards,
Szymon

As I've said, I did contact technical support. So have a lot of people, who've reported no response, as well as to me.

Since I posted this thread, there have been 3 more reports in this forum of issues with DisplayLink on macOS 15.
There is a problem, and it must be acknowledged.

* https://www.displaylink.org/forum/sh...ad.php?t=69602
* https://www.displaylink.org/forum/sh...ad.php?t=69664
* https://www.displaylink.org/forum/sh...ad.php?t=69347

[Szymon]

Thank you for your patience and raising the ticket. I have verified it is now under investigation. Please expect an answer soon. I can confirm that, so far, all user-reported issues initially suspected to be '15.x-specific problems' have led to a variety of different resolutions.

Regards,
Szymon