Question Left and right padding not working?

I am trying out the new UI builder since it seemed to be a promising improvement over the old UI system.
But I quickly stumbled across something that doesn't seem to work:

Placing a button inside my UI, I would like to make the button use the left and right padding. I have set the width and height to "auto" and the min-width and min-height also to "auto". Left and right padding is set to 7px so the button should auto-resize to a size that consists of the left padding + text length + right padding. But instead, the button is always stretched across the whole screen width. However, the top and bottom padding seems to work fine. So why is the left and right padding not working as well? Am I missing something here?