Category image spread on products without image and doesn't change later

When we assign an image to a category we get this image spread over all products without images in this category. Not bad, however later, when we assign specific image to a product it won’t appear on a product page, category image remains on a product regardless of fact that a product now has it’s own image.

https://www.ads-software.com/plugins/ecommerce-shopping-cart-by-inventorycom/