Intermittent blackouts

I just bought a pluggable UD-3900. I have a Dell Latitude E7250 laptop. When I use my Dell ST2410 monitor as a second monitor (connected by an HDMI cable), I get yellow lines on the screen and intermittent blackouts. I have tried updating the drivers to no avail. Any ideas for how to get this to work? Or do I need to return the unit for a refund?

Please see my direct response.