There is a shop on Woocommerce. The webmasters panel of Google regularly receives notifications that duplicate titles and descriptions have been found. We look, what is there for duplicates - screenshot:

It turns out that the same product is available at the correct URL (the one that is longer) and at a URL that does not include the main category (in this case / ventilyatory /). And such duplicates are found constantly. Redirects are affixed, but the problem remains.
How to prevent such duplication?
WordPress 4.1, Virtue Theme, Woocommerce 2.4.7