Thanks for posting!
Just a few quick notes…first, we also received the direct inquiry you sent to http://plugable.com/support/email/ but I am only replying here to help keep all communication in one place and for the benefit of anyone else following this thread.
Second, we actually don’t recommend our USB 3.0 Dual Display Docking station for use on the Mac because of OS limitations that can lead to performance issues (our most recent article on the subject is here if you are curious -> http://plugable.com/2016/09/21/plugab…).
To the behavior with Skype, this is a known issue with applications that require hardware graphics acceleration that DisplayLink (the maker of the chip in our dock and driver author) speak to here -> http://support.displaylink.com/knowle…
That said, the next release of macOS (version 10.13 known as ‘High Sierra’) when used with a future release of the DisplayLink driver will support hardware graphics acceleration on certain Mac systems, and that may resolve the Skype issue. DisplayLink speaks to these updates in their support forum here -> http://www.displaylink.org/forum/show… and here -> http://www.displaylink.org/forum/show…
The workaround for the interim (as you have already discovered) is to run Skype on the internal laptop display.
Please let us know if that information helps!