Plugable USB-C Displaylink PC slow down.

I have a Plugable USB-C Displaylink dock with a 1920x1080 HDMI monitor connected to my DELL XPS 15 9650 (top spec)

I’m trying to edit some video in Premiere Pro cc and the machine is running noticeably slower. As soon as I unplug the USB-C/Displaylink hub the machine returns to full speed (with HDMI monitor now connected directly to computer)

Any ideas how to resolve this?

Many thanks.