Surface Dock 2 would only work with 1 external monitor

New to the community, apologize if I unintentionally did something wrong.

I'm starting to deploy Dock 2 due to the allure of  USB type C.

For some reason none of the four Dock 2 that I deployed would work with dual external monitors.

I tried different brand monitors, different cables type and brand (USB C to DP and USB C to HDMI), combination of different ports (E.G. 1 pluged into HDMI the other DP), different surface device (Laptop 4, laptop 2, Pro 6, etc.), upgrading driver and firmware on both the device and the dock, but only one of the external monitor would work. Interestingly as soon as I turn off/unplug the working monitor image would pop up on the the monitor that was not working. I also made sure the frequencies is set to 60Hz. 
Anybody experiencing this? or better yet knows a solution? 
Thank you in advanced.