This makes it possible to connect to VGA, DVI, or HDMI devices with the use of an adapter. However, to work with a DVI input you must use an active DVI adapter. Using a passive DVI cable will not work.
I tried using a passive DVI cable to connect to my Dell IN2020M monitors. This results in the monitor displaying an error message: “The current input timing is not supported by the monitor display. Please change your input timing to 1600×900@60Hz or any other monitor listed timing as per the monitor specifications.“
I found the gofanco Gold Plated Mini Displayport to DVI Active Converter on Amazon works well with the Surface Dock and I am now driving my two monitors with a good stable image.