A read-only check of 18 category pages found 106 blank image-card occurrences across 67 products. In 94 occurrences, WooCommerce already returned a valid product image; the rendered category HTML still emitted an empty img src. On the Smart BLE category, the 12V PIR product has a valid WooCommerce image but renders blank.
Update the category card to use the WooCommerce featured image when the custom image field is empty. Test the Smart BLE category and representative categories before changing cache settings.