Maybe you’ve already seen these threads,
Yes I’ve been giving this a bash for around 4 days now convinced I am doing something wrong and I’ve trapsed the forums, answerhub and google quite abit!
it’s better to just create a bool that you set in press and release (i.e. bLeftMouseHeld), then setup the functionality you’re looking for in either the actor’s tick or possibly in a separate timer.
This was my initial attempt, but could not find a way to read touch position per frame… The Touches array in PlayerInput (in the PlayerController class) only set their positions when they are first pressed but don’t update after that. And tried various other methods (mentioned in my original post). So quite stumped on how to read this information per frame for touches 
What’s even more confusing is that this code works in a standalone build but not in editor!
That said, I can’t imagine why it starts to behave that way when dragged off the screen. That does, indeed, sound like a bug.
Recon it’s worth me posting this in the bug section?
Thanks for the reply,
Nick