I run dual monitors in a Vertical layout so my main one is at the bottom and the 2nd one is above. I like to put Spotify on my 2nd monitor (Top) while working on my 1st monitor (Bottom). If I drag Spotify to the 2nd monitor (Top) and click full screen it then continue my work on the 1st monitor (Bottom) Spotify doesn't notice the mouse pointer has left the window so it never correctly full screens.
Please see attachments. The first attachment is Spotify running full screen correctly on my 1st monitor, the second attachment is Spotify on my 2nd monitor but not correctly full screen.