I'm not sure what chip they use in these, is there a way I can find out? This is the hardware ID string in my device manager:
USB\VID_17E9&PID_0252&REV_0144
The manufacturer says this is normal behavior and took a picture for me showing the same banding, so it could just be the nature of the DisplayLink compression. Here's a couple pictures to illustrate the difference between a normal display of a gradient and how it appears on my DisplayLink screen.
normal:
http://i.imgur.com/X8POv.jpg
tablet:
http://i.imgur.com/n3CL7.jpg