132UE-TB4USB4DOCK – External displays go black 3 seconds after wake on MacBook Pro M1 Pro

[drego85]

Hi,
I am experiencing a reproducible display issue with a StarTech 132UE-TB4USB4DOCK connected to a MacBook Pro with Apple M1 Pro.

The dock works normally during regular use. The problem occurs after the displays have gone to sleep.

My normal setup is:

• MacBook Pro with Apple M1 Pro
• StarTech 132UE-TB4USB4DOCK connected via Thunderbolt 4
• Two external LG displays, both connected to the dock via HDMI
• MacBook normally used in clamshell mode
• Apple USB keyboard connected through the dock
• Ethernet and an external USB-C drive also connected to the dock
• Power Delivery provided by the StarTech dock

The issue is consistently reproducible with the following sequence:

1. Everything is working normally and both external displays are active.
2. I lock macOS and wait for the displays to turn off.
3. I wake the Mac using the external keyboard and unlock it.
4. Both external displays initially wake up and work normally.
5. Approximately 3 seconds after wake/unlock, both external displays go black.
6. Power-cycling the StarTech dock immediately restores normal operation.

I performed several tests to determine whether this was a macOS sleep issue or a loss of the Thunderbolt connection.

The Mac itself does not go back to sleep.

I repeated the test with the MacBook lid open. When the problem occurred, the built-in MacBook display continued to work normally and the session remained unlocked, while only the displays connected through the StarTech dock went black.

macOS still detects the external displays while they are black.

During the failure, System Settings > Displays continues to show both external monitors. I also captured system_profiler SPThunderboltDataType SPDisplaysDataType while the problem was occurring. Both LG displays were still reported as: Online: Yes

The StarTech dock was also still detected and the Thunderbolt/USB4 connection remained active at 40 Gb/s.

Other dock functions, including USB devices and Ethernet, also continue to operate. Therefore, the dock itself does not appear to disconnect from the Mac; only the video output stops working.

The problem also occurs with only one HDMI display connected to the StarTech dock.

I disconnected one of the two HDMI displays and repeated the test. The remaining display still became black approximately 3 seconds after wake. Therefore, the problem does not appear to require a dual-display configuration.

I then performed an A/B test using another dock that I previously used with this Mac: a Kensington UH1400P USB-C dock.

I connected:

• one external display through the StarTech 132UE-TB4USB4DOCK;
• one external display through the Kensington UH1400P;
• both docks to the same MacBook Pro at the same time.

I then repeated exactly the same lock/display-sleep/wake procedure with the MacBook lid closed.

After wake:

• the display connected through the Kensington continued working normally;
• the display connected through the StarTech became black after approximately 10 seconds.

The MacBook remained awake and usable through the display connected to the Kensington dock.

This is particularly relevant because, before purchasing the StarTech dock, I used two Kensington UH1400P adapters simultaneously, one for each external HDMI display, with the same MacBook and the same monitors. I did not experience this wake issue with that configuration.

I also checked the StarTech dock information reported by macOS. system_profiler currently reports:

Product: 132N-TB4USB4DOCK
Mode: USB4
Firmware Version: 41.1
Micro Firmware Version: 0.88.0
Link Speed: 40 Gb/s

I would therefore appreciate your help determining whether this is a known sleep/wake or display reinitialization issue with the 132UE-TB4USB4DOCK on Apple Silicon/macOS, and in particular:

• Is firmware 41.1 / micro firmware 0.88.0 the latest firmware available for this dock?
• Are there any firmware updates addressing display wake, HDMI output, DisplayPort tunneling, or Apple Silicon compatibility?
• Is there any diagnostic information I can collect from macOS while the dock is in this failed state that would help your engineering/support team investigate the issue?
• Are there any known compatibility issues with this dock and Apple M1 Pro systems after display sleep?

I can reproduce the issue consistently and would be happy to provide system_profiler output or perform additional diagnostic tests if required.

Thank you.

[EmmanuelB]

Hello @drego85 and thank you for your interest in our Community.

Thank you for the extremely detailed testing and information. The tests you have already performed are particularly useful in narrowing this down. Based on what you have described, the problem appears to be isolated more specifically to the video output being reinitialized after display sleep.

There are a few additional tests that would be particularly useful:

1. If one of the LG monitors has DisplayPort, connect a single display to one of the dock’s DisplayPort outputs instead of HDMI and repeat the same sleep/wake test. This would help determine whether the behavior is specific to the HDMI video path.

2. When the HDMI display becomes black, disconnect and reconnect only the HDMI cable from the dock rather than power-cycling the complete dock. Please let us know whether this immediately restores the image.

3. Have you tested with different ports on your MacBook?

Could you also confirm the exact macOS version and build number, as well as the model numbers, resolution, and refresh rate of the two LG displays?

Thank you again for the thorough troubleshooting.

Emmanuel B.
StarTech.com Support

[drego85]

Hello Emmanuel,

thank you for your reply and for the additional troubleshooting suggestions.

I performed the requested tests and can provide the following information:

• Both external monitors are LG 23MP65, running at 1920×1080 @ 60 Hz.
• Unfortunately, these monitors do not have DisplayPort inputs, so I am unable to test the dock’s DisplayPort output directly.
• I tested the StarTech dock connected to all three USB-C/Thunderbolt ports on my MacBook Pro, and the behavior is exactly the same on every port.
• I am currently running macOS 27.0.1 (Build 26A434).

I also performed the HDMI reconnect test you suggested, and the result is particularly interesting.

After waking and unlocking the Mac, the external display initially works correctly, but approximately 3 seconds later it goes black.

While the display is black, the Mac itself remains fully awake and unlocked. At this point, I can immediately restore the image in either of these two ways:

1. Disconnect and reconnect only the HDMI cable from the StarTech dock, without power-cycling or disconnecting the dock.
2. Turn the LG monitor off and back on, without touching the dock or the Mac.

In both cases, the image immediately returns and the Mac is already awake and unlocked.

This seems to indicate that the Thunderbolt/USB4 connection and the Mac itself remain operational, while re-triggering the HDMI connection/handshake is sufficient to restore the video output.

As mentioned in my original report, macOS also continues to detect the external display while it is black.

Please let me know if this behavior helps narrow down the issue further, or if there are any additional tests or diagnostic logs I can collect while the display is in the black-screen state.

Thank you again for your support.

Best
Andrea

[EmmanuelB]

Hello @drego85 , thank you for your time and, again, the excellent information provided.

Considering the nature of this issue, I have sent you a contact email in order to continue this investigation under our Support. Your case number is: CAS-265137.

We look forward to hearing back from you!

Emmanuel B.
StarTech.com Support