Monitor on 4K port turns on/off until UD-ULTCDL rebooted

I have just purchased a Dell XPS 13 and I’m having the EXACT problem described in this thread with my UD-ULTCDL docking station. Was a cause for this problem ever determined?

Original post:

After my laptop (Dell Latitude 7490) goes into screen lock (after sitting for 15 minutes…not to sleep, just locks the screen and screen goes blank), the monitor blinks off/on (you see “no HDMI input” then the screen goes off…then comes on again with the “no HDMI input” message…repeat).

Most times, when you move the mouse/keyboard the screen wakes up and all is good. However, 50% of the time the screen continues to blink. The ONLY thing that fixes it is to reboot the docking station.

Pertinent info:

  • The port with the issue is the primary HDMI 4K port (but using a 1080 monitor)
  • This happens whether 1 or 2 monitors is attached (one to the 4K HDMI port and one to the other HDMI port)
  • When 2 monitors are attached, the second monitor (attached to the non-4K HDMI port) works fine even though the first monitor (connected to the 4K HDMI port) continues flashing
  • I’ve switch monitors so it’s not the monitor
  • I’ve turned the monitor off and on but this doesn’t help (monitor still flashes)
  • I’ve unplugged the HDMI cable but this doesn’t help (monitor still flashes)
  • I’ve replaced the HDMI cable but this doesn’t help (monitor still flashes)
  • I’ve disconnected the laptop from the docking station and reconnected but this doesn’t help (monitor still flashes)
  • I’ve rebooted the laptop and this doesn’t help (monitor still flashes)
  • I’ve rebooted everything (monitors, laptop, wireless mouse, keyboard) at the same time but this doesn’t help (monitor still flashes)
  • The ONLY thing that fixes it is to reboot the docking station.


Thank you for contacting Plugable support! Sorry to hear about this issue. I’d be more than happy to assist you.

This kind of issue can have multiple different causes and solutions. What may have helped in the other situation linked to may not be solved in the same way here. It would be best for us to get some diagnostics from your computer to determine the next course of action. Which is what was done with that other situation. Ultimately in that scenario I believe we needed to send a replacement under warranty - however, more often than not these issues can be resolved via software.

Worst case scenario if nothing appears to be wrong in the software or our suggestions do not help, we can next issue a pretested (known good) replacement docking station under warranty to try and rule out any hardware issues.

To start, we have a troubleshooting tool that helps us find out what is going on in situations like this. If able, please plug the dock with your monitors and other devices attached to it into your computer, then go to this page and follow the instructions there:

When emailing us the diagnostic results .zip file that is generated to as an attachment, please mention ticket #364730 in the email subject line. (Do not post the attachment here.)

I can then take a look at what might be happening and hopefully make some recommendations.

Please don’t hesitate to let us know of other questions.

Thanks again for contacting Plugable support and best wishes!

Joshua Henry
Senior Engineer | Product Owner
Plugable Technologies

Thank you very much for your help. I’ve sent in the debugger output and hope that your techs can determine what the issue is.

You’re most welcome! I’ve received your email and just sent out a reply there.


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