I found an error in block_products_top_sellers.php. On line 72
$sql_params["select"] = "i.item_id, SUM(i.item_id*oi.quantity) AS item_id_counts";
This means that depending on the number of item_id it get higher rated. This is the right line.
$sql_params["select"] = "i.item_id, SUM(oi.quantity) AS item_id_counts";