Ali Datatable Bundle - 在表中搜索时出现Ajax错误（Symfony2）

I get an Ajax error when searching columns in a datatable using Ali Datatable Bundle in a Symfony2 project. The error I get is as follows:

dataTables warning: table id = table - Ajax error.

When I place setSearch(true) the columns that are under "lec" cannot be searched but the columns ncompt.ncomptador and sub.nsubministrament can be searched without getting any ajax error.

Any recommendation?

Here is the code I have placed in the "DefaultController.php" file:

return $this->get('datatable')
    ->setEntityManager($em)
    ->setEntity("AquagestLecturesBundle:Lectura", "lec")
    ->setFields(
        array(
            "ID" => 'lec.id',
            "Any" => 'lec.lecany',
            "Trimestre" => 'lec.trimestre',
            "Lectura" => 'lec.lectura',
            "Consum" => 'lec.consum',
            "Tipus lectura" => 'lec.tipus',
            "Nº de subministrament" => 'sub.nsubministrament',
            "Nº de comptador" => 'ncompt.ncomptador',
            "Edició" => 'lec.id',
            "_identifier_" => 'lec.id'

        )
    )
    ->addJoin('lec.ncomptador', 'ncompt', \Doctrine\ORM\Query\Expr\Join::INNER_JOIN)
    ->addJoin('ncompt.subministrament', 'sub', \Doctrine\ORM\Query\Expr\Join::INNER_JOIN)
    ->setRenderers(
        array(
            0 => array(
                'view' => 'AquagestLecturesBundle:DTActions:checks.html.twig'
            ),
            2 => array(
                'view' => 'AquagestLecturesBundle:DTActions:trimestre.html.twig'
            ),
            8 => array(
                'view' => 'AquagestLecturesBundle:DTActions:edicio.html.twig'
            )
        )
    )
    ->setOrder("lec.lecany", "desc")
    ->setOrder("lec.trimestre", "desc")
    //->setOrder("lec.data", "desc")
    ->setHasAction(false)
    ->setSearch(true)