WooCommerce product gallery displaying black line on image

Hi SiteOrigin Support,

I’m using the SiteOrigin North theme with WooCommerce and have come across an image display issue on one of my product pages.

A thin black line appears along the edge of one product image in the normal WooCommerce product gallery. However:

The original JPEG does not contain the black line.
The WordPress-generated 600 × 411 version is also clean when opened directly.
The black line disappears when the image is opened in the WooCommerce lightbox/full-size view.
The issue appears in both Chrome and Safari.
On an iPhone, the line is not visible in portrait orientation but appears when viewed horizontally.
Regenerating WooCommerce thumbnails made no difference.
Changing the WooCommerce main image width made no difference.
Removing the zoom image in Chrome Developer Tools did not remove the line.
Testing border, box-shadow, overflow and fractional gallery-width settings also made no difference.

The affected WooCommerce product ID is 6004.

From the testing I’ve done, it appears the issue may be related to the way the SiteOrigin North WooCommerce gallery/FlexSlider is rendering the image at certain responsive widths, rather than an issue with the image itself.

Would you be able to advise what may be causing this and whether there is a theme setting or CSS fix that could resolve it?

Please see the link below with the black line on the edge of the product.

Sydney Harbour Bridge Wall Art Print – North Sydney Harbour View

Many thanks,

Paul Lovelace