Zend certified PHP/Magento developer

Magento 2.3 Prev/Next Product on Porto theme is not working

I have set the category sort order to ‘position’ both in store catalog settings and categories settings.
It works fine on category view. However when on a product page the previous/next product link doesn’t have the same order as per the category page.

I’ve come across many post on this saying it comes from Mageplaza/LayeredNavigation but none of the solutions seems to work.

Product position that comes from this code doesn’t get the position stated in category backend :

public function getPrevProduct($product) {
    $current_category = $product->getCategory();
    if(!$current_category) {
        foreach($product->getCategoryCollection() as $parent_cat) {
            $current_category = $parent_cat;
        }
    }
    if(!$current_category)
        return false;
    $cat_prod_ids = $this->getCategoryProductIds($current_category);
    $_pos = array_search($product->getId(), $cat_prod_ids);
    if (isset($cat_prod_ids[$_pos - 1])) {
        $prev_product = $this->getModel('MagentoCatalogModelProduct')->load($cat_prod_ids[$_pos - 1]);
        return $prev_product;
    }
    return false;
}

Does anyone has some insight to share?