On 4.8 (P4), widgets do not accept button clicks when the containing window is not in focus. Here is an example video on OSX using the same screen. The main editor windows is sharing the same screen as the secondary editor window:
In the video, notice that I initially click the play button in each window that doesn’t have focus. The editor does not play. When I click in a window that doesn’t have focus and then click again, the editor responds. This is the same behavior in either window.