You export your products and you get an error message like this one:
Duplicate EAN codes for products, References: [2/7, 2/8, 2/9, 2/10, 2/11, 8/48, 8/49, 8/50, 8/51]
It is a list of product and combination identifiers, in the format 1/2, 1 is the product ID, and 2 the combination one.
Each concerned product contains a duplicate EAN, that means that the EAN code of the product is present two or more times in the database, which is wrong.
Common example of duplicate EAN code:
You must ensure that each product and each combination has a unique EAN code as shown on the page: validate your catalog structure.
You can then find a product displayed in this list of identifiers, through its Product ID by searching in your catalog, for example: