Workaround until this is fixed: Whenever this happens, you can still move the window. Alt+Tab to regain focus outside of the window and then find the program's icon on the Windows Taskbar. Hover over it with your cursor and then the preview window will appear above it. Right-click this preview window and select "Move". Press any arrow key and then move the mouse cursor. The window should become anchored to the mouse and allow you to move it.
When changing a packaged game from Fullscreen to Windowed mode at runtime, the window is placed in the top left corner of the monitor and the title bar disappears.
Setting FullscreenMode=2 in the GameUserSetting.ini seems to resolve this issue; however, this is inconsistent with the behavior in 4.11.2.
This issue did not occur in 4.11.2. As a result, it is a regression.
Result: The window becomes stuck in the top left corner of the monitor and the title bar disappears.
Expected: The window would appear centered and would not lose the title bar.
4.13 Preview 1 Repro Steps:
Result: The window becomes stuck in the top left corner and the title bar disappears.
Head over to the existing Questions & Answers thread and let us know what's up.