I am having what sounds like a very similar issue with my TBT3-UDV dock. I have it hooked up to a Dell XPS 13” 9350 laptop. I have two HP 24ES monitors. One connected using the included DisplayPort to HDMI adapter and the other using USB-C to HDMI (plugable brand) adapter which plugs into the doc.
I will be in the middle of using the system and all of a sudden both screens go black and you can hear the common windows sound when you disconnect a USB device. Then after a few seconds it comes back and USB devices are recognized again and the screens come on. However sometimes the screen will return and shake back and forth or be screwed off the screen.
The only way to fix it is to unplug the thunderbolt cable from the laptop and reconnect it again or reboot but this only lasts for a few minutes. It is essentially unusable . I have also tried running with a single monitor and have the same issue.
My laptop has the latest Bios for Pc and thunderbolt conteoller and the latest thunderbold drivers and I am using the cable that was supplied (which is pretty short I might add).
I have had the dock since March 28, 2018 and can return it until April 28, 2018. Hoping you can resolve this issue or else o will be returning it and going with the Dell dock… according to your site this laptop should be compatible.
On another note I connect my HP Elitebook x360 G2 and it only sees the monitor that is plugged into the DisplayPort. Not sure if it is a limitation of the HP thunderbolt but in my office I have a dual screen setup working with the HP USB-c dock with no issue.