Monitor blinking on HDMI port of TBT3-UDC3 with MBP 16"


I have MacBook Pro 16 and bought TBT3-UDC3. Connect only Plugable power adapter and two monitors. First is 4k/60Hz LG 27" through DisplayPort. Second is 1080p/60Hz Philips 224E5 through HDMI.
LG working fine, but second monitor with 1080/60 is blinking after waking up.
If I change refresh rate to 50Hz temporary and return to default 60Hz, monitor work fine to next sleep cycle.
I have recorded video -

Hi @superkent,

Thanks for posting!

I appreciate you taking the time to shoot that video of the problem. As a temporary test, would it be possible to swap the video connections between your LG and Philips monitor to the TBT3-UDC3 dock?

In other words, please connect the LG monitor to the HDMI port on the dock, and connect the Phillips monitor to the DisplayPort port on the dock. When that is done, does the blinking follow the HDMI port, or the HDMI cable?

We’ll be able to better take the next steps from there.

Thanks for giving us a chance to help!


I cannot connect Philips to the DisplayPort because it doesn’t have. But I will connect through HDMI<->DP adapter.

LG I have connected with another cable.
So Philips connected to DP port through HDMI adapter, LG connected to HDMI port.
nothing has changed, LG now blinking -

Summary - port HDMI is broken and work after changing software config.

Got it, thanks for trying.

Could you please reach out to us at with your Amazon Order ID? You may include “Ticket #336775” in the subject line so that we can match it up to this post.

We’ll be able to better help from there.



I have did it. But I sent two emails, sorry.

Please post here with final resolution. I (and many others) have had similar issues with the HDMI connection on this dock and would love for a solution from you guys in form of a firmware update…

As an update to this post, the original poster reached out to us directly and we provided an firmware update utility in which we were able to update the firmware of the TBT3-UDC3 dock with a Thunderbolt 3 Windows host, which has resolved the HDMI flickering issues.

@eysun, do you have a Thunderbolt 3 or USB-C compatible Windows computer? If so, we’d be glad to post these same instructions here for you.

If not, please reach out to us at with your Amazon Order ID. We’d be glad to send you a warranty replacement dock flashed with the latest firmware.



Yes, I do have a USB-C compatible windows computer. Would bootcamp on my MacBook work as well?

Great! We haven’t tested a Mac running Bootcamp, so I’m afraid I can’t speak to whether or not that will work.

To update the firmware in the dock, please follow these steps:

Please let me know if that update is successful and if it helps with your Mac!



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Landed here with the same blinking HDMI issue. I successfully flashed the firmware to 5.05.202 and the issues persisted. I then switched to display port. Via DisplayPort, rather than just the monitor flashing out for a few seconds, the entire dock acts like is disconnects. I hear the disconnect tone, everything goes black, then the reconnect tone, and everything comes back(although now windows are all rearranged on difference monitors. Using a Lenovo Thinkpad X1 extreme gen 20QVCTR1WW. Using built in laptop display 1080p 60hz and external monitor is Dell u2781Q @ 4k/60zh

Please advise.

Hi Josh,

Thanks for reaching out.

The fact that the entire dock is disconnecting could signal a different issue. Could you please reach out to us at with a set of log files captured through our PlugDebug tool?

We’ll be able to better assist from there.




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