Entity's association changes after first call

i am using the latest version of doctrine: 2.3

when you call a generated association function, the first time everything is fine:

$authors = $book->getBookToAuthors();
//$authors = array(5)
but the second time instead of returning the array of all associations it returns the last hydrated entity:

$authors = $book->getBookToAuthors();
//$authors = BookToAuthor entity
that happens even when there is nothing else happening:

$authors = $book->getBookToAuthors(); //will work
$authors = $book->getBookToAuthors(); //won't work
the function of getBookToAuthors() is:

public function getBookToAuthors()

and the mapping is as follows:

/**

• @var BookToAuthor[]
  *
• @OneToMany(targetEntity="BookToAuthor", mappedBy="book", cascade= {"persist"}

  )

• @JoinColumn(name="id", referencedColumnName="book_id", onDelete="cascade")
  */
  private $bookToAuthors;
  please advise. i don't know what to do...