Maybe you’ve already seen these threads, but between these and my own experience with this, 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.
As far as I know, IE_Repeat is primarily for keyboard input, because keystroke input actually does repeat; if you hold down the “q” key, a line of q’s will output. Mouse clicks, to my knowledge, don’t function like that- they only have the two states. 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.