Ahhh... A bug in my submission...
My submission has a bug related to game over screen where some actor doesn't disappear in game over state in specific situation. But I cannot reproduce and debug it inside Unreal Editor. The bug appears only in the packaged build.
Now I'm thinking that next time I should use only Visual Studio to make a game using Unreal Engine. Making Games with Unreal Editor and Blueprint scripting still needs long times for enhancement...