Mouse capture gets caught by default created PlayerController

In PIE games, it looks like this may be caused by the window immediately taking control of the mouse and setting up focus.

In networked games, clients call ULocalPlayer::SpawnPlayActor which will create a default APlayerController (unless otherwise configured). This later gets deleted, but may have previously set focus.

1. Create a UCLASS with a BP function to release mouse capture (see below).
2. Start QA Game.
3. Open any map (including the default empty map).
4. In the level BP, tie the release mouse capture function to some input key.
5. Launch in mobile preview.
6. Move the mouse around.
7. Call the release mouse capture function.
8. Move the mouse around.

EXPECTED: Before and after the release mouse capture function is called, the camera does not change unless you grab the left virtual joystick.

ACTUAL: The camera changes and tracks the mouse before the release function is called. After the function is called, it works like expected.

UCLASS()
class UMyClass : public UObject
{
    GENERATED_BODY()
public:

    UMyClass(){}

    UFUNCTION(BlueprintCallable, Category="Mouse")
    static void Release()
    {
	FSlateApplication::Get().ReleaseMouseCaptureForUser(0);
    }
};