on the webassist/plugins/catalog/results.php and results_grid.php pages, change the WADAProducts recordset code:
$query_WADAProducts = "SELECT *, coalesce((select ps4_productoptions.GroupingID from ps4_productoptions WHERE ps4_productoptions.ProductID = ps4_products.ProductID limit 1),ps4_products.ProductID) AS GroupingID FROM ps4_products WHERE ProductLive = 1 AND (ProductStartDate IS NULL OR ProductStartDate <= CURDATE()) AND (ProductEndDate IS NULL OR ProductEndDate >= CURDATE()) GROUP BY GroupingID ORDER BY ProductName";
to use ORDER BY ProductSKU, instead of ORDER BY ProductName :
$query_WADAProducts = "SELECT *, coalesce((select ps4_productoptions.GroupingID from ps4_productoptions WHERE ps4_productoptions.ProductID = ps4_products.ProductID limit 1),ps4_products.ProductID) AS GroupingID FROM ps4_products WHERE ProductLive = 1 AND (ProductStartDate IS NULL OR ProductStartDate <= CURDATE()) AND (ProductEndDate IS NULL OR ProductEndDate >= CURDATE()) GROUP BY GroupingID ORDER BY ProductSKU";