animate()で上端までスムーズスクロールしたあとにスクロールがしばらく効かなくなります。

[html]

<!DOCTYPE html>
    <html xml:lang="ja" lang="ja">
    <head>
    <meta charset="utf-8">
    <title>jQuery TechnicalNote － SAMPLE</title>
    <link rel="stylesheet" href="../../common/css/common.css">
    <link rel="stylesheet" href="css/style2.css">
    <script src="../../common/js/jquery-1.11.3.min.js"></script>
    <script src="js/script2.js"></script>
    </head>

    <body>

    <header class="baseHeader">
    <div>
    <h1>jQuery TECHNIQUE</h1>
    <a href="../../chapterList.html">&gt;&nbsp;CHAPTER LIST</a>
    </div>
    </header>

    <div id="wrapper">

    <p>現在のスクロール値：<span>0</span></p>

    </div><!-- /#wrapper -->

    <footer class="baseFooter">
    <small>Copyright &copy; SB Creative Corp. All Rights Reserved.</small>
    <footer>

    </body>
    </html>

[js]

$(function(){
        $(window).on('load scroll resize', function(e){
            var scrollTop = $(window).scrollTop();
            $('p > span').text(scrollTop);
            console.log(scrollTop);

        var posBottom = $(document).height() - window.innerHeight;
        console.log(posBottom);
        if(scrollTop >= posBottom) {
            //$('p').addClass('scrollBottom');

            e.preventDefault();
            //戻る
            $('body').animate({scrollTop:0},2000);
            console.log('scroll!');

        } else {
            // $('p').removeClass('scrollBottom');
        }
    });
});