Counterfeit Duracell AA and AAA batteries are widely available and can lead to quality and performance problems.
Duracell batteries are so well-known and respected, so widely available and so standardised that it is perhaps inevitable that they will be counterfeited. But beware, the myth that all batteries are the same is far from true. The major manufacturers carefully guard the reputation of their products and the consistent quality of the many billions of batteries they supply annually.
There have recently been a number of news stories about exploding batteries and trading standards finding higher than normal levels of counterfeit product available for sale.
Please be sure of your source of supply. Do you deal with a supplier that has a direct relationship with the manufacturer? Do you know that you are supplied with fresh product fully backed up by the manufacturer's guarantee?