The window's content gets clipped when the window goes from Maximized to Normal WindowState. This reproduces only when the window and the screens are using specific sizes. The setup when this was reproduced was with a 1936x1056 size of RadRibbonWindow (in Normal state) and 1920x1080 screen resolution.

To reproduce this the IsWindowsThemeEnabled property of the RadRibbonWindow should be set to False.

To work this around, reset the Window size on WindowStateChanged.

private void MainWindow_StateChanged(object sender, EventArgs e)
{
	if (this.WindowState == WindowState.Normal)
	{               
		Width += 1;
		Width -= 1;
	}
}