Symfony2 and Doctrine: OneToMany relation duplicates data in the table

I have two tables: articles and emails. The emails table will contain emails related to the specific articles, for example:

id    |  article_id |     email
1     |      1      |  test@etest.com
2     |      1      |  test2@test.com
3     |      2      |  test@etest.com
4     |      2      |  test3@test.com

Etc....

There is a relation between article_id and the id from the articles table.

In my entity, I have this code:

class Articles
{ 
    ....
     /**
      * @ORM\OneToMany(targetEntity="\Acme\DemoBundle\Entity\Emails", mappedBy="articles")
      */
      private $emails_rel; 

    ...
}

class Emails
{ 
    /**
     * @ORM\ManyToOne(targetEntity="\Acme\DemoBundle\Entity\Articles", inversedBy="emails_rel", cascade={"all"})
     * @ORM\JoinColumn(name="article_id", referencedColumnName="id")
     **/
    private $articles; 
}

In my controller, i am doing some tests where I will persist or not some entities. At the end, I am doing a flush

$em->flush(); 

And the strange behaviour is that in my Emails table, the data is duplicated as soon as I am doing the flush. When testing the entity manager with

$em->getUnitOfWork()->getScheduledEntityInsertions()

I am getting an empty array.

Any idea why? Thank you very much.

EDIT:

Here is the test:

$articl = new Articles();
$articl = $em->createQuery("SELECT p FROM Acme\DemoBundle\Entity\Articles p WHERE p.bMailToMatch = 1")->getResult();
$nb = count($articl);

// BECAUSE I WILL WORK WITH A LOTS OF ENTRIES - PREVENT MEMORY OVERFLOW
$em->clear();    

if(isset( $articl )) {
    foreach($articl as $i => $art) {
        $array_emails = null;

        $art_emails = $art->getEmailsRel();
        foreach ($art_emails as $e) {
            $array_emails[] = $e->getEmail();
        }

        $art_id = $art->getId ();
        echo "\n\n---------- $i ----------\n " . $art->getDoi ();

        // TAKES ARTICLE WITH ZERO EMAIL
        if (!isset($array_emails) ) {
            $updated_article = $em->getRepository('AcmeDemoBundle:Articles')->findOneBy(array( 'id' => ($art_id)    )) ; 
            // Because of the clearing of the entity manager
            echo"\n\n$art_id Article DOI \n".$updated_article->getDoi();
            echo "\n==>Put the BMailToMatch's flag to 0";
            $updated_article->setBMailToMatch(0);
            $em->persist($updated_article);
        }
        else {
            echo " ==> ok\n";
        }

        if (($i % 3) == 0) {
            $em->flush();
            $em->clear();
        }
    }

    $em->flush();
    $em->clear();
}

return new Response ( "\n\nFinished!!\n" );