You can reproduce the issue by starting the game as standalone from the editor and double tapping the tilde console key to bring up the full console window. You’ll notice “LOST FOCUS” printed on the screen. However, if you alt-tab from the game window itself, lost focus does not fire and the text is not printed to the screen.
This is all done via C++ by extending GameViewportClient(To override LostFocus) and GameInstance (for a global event broadcast).
Lemme know if you need more information from me, thank you for the prompt response!
After opening the project I found that the source file was missing and I was unable to open the project. Could you zip down the project again and make sure to include the Content, Config, Source, and Uproject are included?
We were able to reproduce this issue on our end. I have written up a report ( UE-22128) and I have submitted it to the developers for further consideration. I will provide updates with any pertinent information as it becomes available. Thank you for your information and time.