Hello Simon, thanks for posting! I am sorry to hear of this strange behavior and I will be happy to help.
Thank you for the description of what you are seeing. Based off of this we will want to reinstall the DisplayLink drivers and run the DisplayLink cleaner tool to make sure that the software used by the DisplayPort ports on our dock is in a good state. To do so, please follow these steps:
Disconnect the dock from the system and please remove the power cable from the dock so it turns off completely (this is important so the unit resets). Please keep it disconnected until the last step.
Uninstall any and all software with ‘DisplayLink’ in the title that is present from within the Control Panel -> Programs and Features. Don’t worry if these entries are not present or if the process does not work, just move onto the next step
Reattach the power cable to the dock first. Once the dock is powered on, reconnect it to your system which will trigger the final portion of the installation. If the device is not detected, please click the ‘Skip’ button to allow the process to complete and then reboot the system.
Please let us know if these steps help or not and we will go from there.