I want to be able to use a Scroll Box with a vertical List or whatever that does not force a size. This is not posible in 4.12
This is still a bug in 4.14
Still a bug, apparently. I’m having similar issues trying to make a scrollable menu with several vertical boxes.
Okay I just wanted to put my two cents in here. 
I just had this issue and come to find out that the other items in the widget in order were set to visible and everything in front of that part of the widget (borders, boxes, etc) needed to be set to Hit Test Invisible or Self Hit Test Invisible. Once doing this it worked! I was able to scroll.
I know it’s been many years but I’ve had similar problems. I have made a post that I think is a good solution to the problem: Problem resizing the game window - menu deforms - scroll box pops out (solution)