(Bug) a part of window put on between two monitors is invisible !! (Yosemite)
Bug report (Yosemite)
When I move a window from a monitor to "between" two monitors,
Ver 2.3 to be invisible "destination side" window
Ver 2.4b1 to be invisible "source side" window
This is serious bug, so please improve at once.
See the comment from Carlo on this being an OS X feature, which can be disabled.
Mavericks has introduced the notion of "displays as spaces". This is not specific to DisplayLink screens and implies that a window can only be on one screen at a time. When placing a window between two screens, the window will only be drawn on the screen that has the most important part of the window on it.
To disable this feature go to the Mission Control preference and disable "Displays have separate Spaces". This however will also disable other handy features like the menu bar on all screens.
You may want to ask Apple to improve at once by using bugreport.apple.com.