Windows move back to main monitor after screens lock

I have the UD-CA1A USB hub attached to a Dell XPS 15 laptop via the usb-c port.
I have a monitor connected via the HDMI cable on the hub.
The second monitor works fine except when the laptop has been locked for a short period and I log back in.

At this point the windows I had open on the second monitor will have returned to my main laptop display. I am guessing because the second monitor has gone into power saving mode and the laptop reverts to a single display setup.

This doesn’t happen if I plug the display directly into the laptop HDMI port.

Is there a way to stop this happening

Hello Peter, thank you for posting. I am sorry to hear of this behavior and I will be happy to help.

Just to clarify, does the monitor connected to our dock display your Desktop when waking your system from sleep/being locked, but the programs you expect to be open on the screen moved over to your laptop screen?

Assuming that is the case and based off of your description, there could be a few different variables that contribute to this behavior. We’d like to examine some log files from your system to determine what could be happening. To help us do so please download and run our diagnostic utility PlugDebug --> just after the behavior has occurred. Please send us the file that is created on your Desktop by attaching it to an email to our direct support email address at with ‘Ticket Number 210357’ in the Subject Line. We’ll match everything up, examine the logs and determine next steps from there.

Thank you,

David W.
Plugable Technologies