App always opens in fullscreen on Windows 10

Hi there,

we have an app that always opens in fullscreen on Windows 10 and can´t be resized. Other apps that use the same monogame version (3.5) are opening in a window on windows 10 and not fullscreen like on windows 8 or 8.1. I remember that we got a message from microsoft when windows 8.1 was out that the resize-functionality doesn´t work correctly (like if you have a splitview of the app and it´s just half of the screen and you can´t click on anything).
Could it be that Microsoft forces those apps (maybe checks the packagename) to be fullscreen on windows 10 to prevent any user complains?
Things like “graphics.IsFullScreen = false;” don´t work.