Hi there, Flatted5!
Thanks for reaching Microsoft Community. We are sorry to learn that you have issues with the external displays whenever it is connected to the Surface Pro 7 via USB-C or Surface Dock.
I want to ask questions so we can clarify and understand the situation better.
-What is the brand and model of the external displays?
-What type of cable did you use and its length?
-Are your devices plugged into the wall outlet, extension, or surge protector?
-Are those monitors using HDMI?
Looking forward for your response.
Regards,
Janette_Z