Thanks for reaching out.
It is column border which showing in that way while the columns are in a separate row, it has been found that it goes in a separate row for the 1200px width. I would suggest you add the following custom CSS code into the ELement CSS of the parent Row of the columns to get rid of the border below 1200px screen size. You may need to adjust the screen size within the media query for 1200px.
@media (max-width: 480px)
Please remember that the above code will work if copied as it is and doesn’t conflict with any existing style.
Please note that the code provided serves only as a guide to help you get started custom coding on your own if there’s no option offered in our theme or the products we bundle.
We really do not provide support for custom codes that means we can’t fix it in case it conflicts with something on your site nor will we enhance it.