There is a difference between Sold Out, products_quantity <= 0, and Out of Stock, products_status = 0 ...

If you want to never see Sold Out Products on your site, you need to change the settings in Configuration ... Stock Settings ... so that out of stock products have the Product Status, (products_status) set to 0 on an Order ...

If you want to show Sold Out Products but not show them in the New Products ... then you need to customize the code for the Centerbox, Sidebox and New Product listing to not include Products with a products_quantity <= 0 ...

NOTE: The bug in v1.3.8, was where the Products with products_status = 0 were still showing ...

NOTE: to set products_status = 0, when Products are Sold Out on an Order, you would need to update the existing Products as this is only controlling new Orders on the check out ...