On a multiscreen system, when InDesign starts up on the Dell Canvas drawing tablet screen, the window can't be moved to any other screen in the system. If the Dell Canvas is turned off then on, InDesign automatically moves to another screen. At that point, the window can be moved to any other screen in the system. However, if you move it totally onto the Canvas screen, it will be pinned to that screen, unable to move back to the other screens.

InDesign 15.01 x64. Dell Canvas screen is the primary screen for windows. Other monitors are 32" 4k+ monitor and 28" 4k monitor. Adobe Acrobat Pro DC does not have this problem so this is an InDesign problem.