Intermittent issues with displayport

Macbook pro 2018 with 10.14 Mojave. Main monitor plugged into displayport and another monitor through second TB port with HDMI adapter, usually with laptop closed. System works fine for a while, and then the displayport monitor will lose signal intermittently. Also sometimes does not regain signal from sleep, need to open laptop and close again.

Works fine with only a single monitor plugged into TB port with HDMI adapter.

Hi Michael,

Thank you for posting, and I would be happy to help with your docking station.

Based on your description, a few quick questions for you:

  1. Can you confirm that you are using only the Thunderbolt 3 cable we included in the box with the dock to connect it to your laptop? I ask because other cables can sometimes cause problems.

  2. Can you let me know the brand and specific model number of the display affected by the problem? I would like to look up its specifications online.

  3. Can you confirm that you are using a standard DisplayPort to DisplayPort cable (a cable with a DisplayPort connector on both ends) to connect the display to the dock? It sounds like that is the case, however I just want to be sure I understand how things are connected.

  4. If you replace the DisplayPort cable with a different/new one (should you have one available), does that change the behavior? Apologies if the request appears redundant, however in similar cases the cause was determined to be the video cable itself, so I would like to rule that out here if possible.

  5. Can you confirm that the display connected to the dock’s downstream Thunderbolt 3 port using the USB-C to HDMI adapter is never affected by the problem?

Thank you for giving us the chance to help!

Plugable Technologies

Update, it looks to be a problem only when both displays are connected. When 1 monitor connected it works. However need a two display solution.

  1. yes
  2. (main, DP) LG 27UD60, (2nd, TB w/ HDMI) TCL 55S405 55" tv
  3. yes
  4. yes, swapped out cables and no change
  5. both are impacted, it seems that the DP is more flaky

Hi Michael,

Thank you for getting back with the additional information. Based on your responses no obvious causes of the problem jump out, so our next step is to get some additional information from your system.

If you would, please keep everything connected and send the output of our diagnostic utility PlugDebug –> to us directly at with ‘For ticket # 241159’ in the subject line. This will allow us to match things up and examine some log files from your system to help determine the next steps.

** Please also include your Amazon Order ID number for the dock purchase in your direct email. Please do not post the Order ID or the PlugDebug in our public forum. **

Thank you,


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