jquery FormData não aceita retorno json

<?php
    if ( isset($_POST['edtCodigoEmpresa']) ){
        $codigo = explode(';', $_POST['edtCodigoEmpresa']);
        $file=[];
        if (isset($_FILES['upload'])){
            $file = [
                'name'     => $_FILES['upload']['name'][0],
                'type'     => $_FILES['upload']['type'][0],
                'tmp_name' => $_FILES['upload']['tmp_name'][0],
                'error'    => $_FILES['upload']['error'][0],
                'size'     => $_FILES['upload']['size'][0]
            ];
        }

        $output = [
            'codigoempresa' => $codigo[0],
            'codigoestab'   => $codigo[1],
            'referencia'    => $_POST['edtReferencia'],
            'random'        => rand(10000,99000),
            'file'          => $file
        ];
        sleep(1);
        echo json_encode($output);
        exit;
    }
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Teste jQuery Upload</title>
    <script type="text/javascript" src="http://code.jquery.com/jquery-2.2.4.js"></script>
</head>
<body>
    <form id="formArquivoInventario" name="formArquivoInventario" method="POST" enctype="multipart/form-data">
        <p>
            <label for="edtCodigoEmpresa">Empresa</label>
            <select name="edtCodigoEmpresa">
                <option value="0;0">000-TODAS</option>
                <option value="132;1">Empresa 1</option>
                <option value="456;2">Empresa 2</option>
            </select>
        </p>

        <p>
            <label for="edtReferencia">Data (Mês/Ano)</label>
            <input type="text" name="edtReferencia" value="02/2018" class="required datareferencia" maxlength="10"/>
        </p>

        <p id="p_upload">
            <label for="edtArquivoAnexo">Arquivo</label>
            <input type="file" name="upload" class="required" />
        </p>
        <p>
            <input type="submit" value="Enviar">
        </p>

        <div class="br"></div>

        <div id="dialog_relatorio">
            <div id="msg"></div>
        </div>
    </form><!-- fim do form -->
    <script type="text/javascript">
    $(document).ready(function(){
        $('#formArquivoInventario').on('submit', function(e){
            e.preventDefault();

            var formData = new FormData();
            var form = $('form').serializeArray();
            $.each(form, function(key, val) {
                formData.append(val['name'], val['value']);
            });

            var files = $('input[type=file]').prop('files');

            var total_upload = 0;
            for(i=0;i<files.length;i++){
                formData.append('upload[]', files[i]);
                total_upload += files[i].size;
            }

            if (total_upload > 10485760) {
                alert("Tamanho do upload enviado " + total_upload +" excedido!\nMáximo permitido 10mb.");
                return false;
            }

            $.ajax({
                //url: 'submit.php',
                method: 'POST',
                cache: false,
                processData: false,
                contentType: false,
                dataType: 'json',
                data: formData,
                beforeSend: function(){
                    var rand = parseInt( Math.random(1,99999)*1000 );
                    $('#msg').html('Processando... ' + rand);
                },
                success: function(data){
                    $('#msg').html('success: ' + data.random);
                },
                complete: function(data){
                    console.log(data.referencia);
                    $('#msg').html('complete: ' + data.random);
                },
                error: function (  jqXHR, textStatus, errorThrown ){
                    console.log(jqXHR);
                }
            });
            return false;
        });
    });
    </script>
</body>
</html>