Hello, you have not actually tested correctly.
What you have done is add a background image in the column until there correct, then you have added a COLOR for the overlay, what I said was that it doesn't work when you add a PATTERN (an image) for the overlay.
I have duplicated your section, and in the column I selected the Joomla logo as the overlay pattern, in the editor it is visible, but in the public part it is not visible, it does not exist.
Please check it again.
Thanks.
Extra: I am also using version 4.0.6 but in mine there is no duplicate column option, as I saw in your editor. why?