Unable to reload same gif image, if used twice in a page

I am using same gif image twice in a page. Both the images will be hidden initially. Based on certain criteria I am showing those gif images (when clicked on particular target one gif image will be shown at a time). I am unable to reload the gif image. See the attached plunker

1) https://plnkr.co/edit/vqZCHkyq7zCRCLpe9osF?p=preview

    <script>
    var img1 = document.getElementById("img1");
    var img2 = document.getElementById("img2");

    function toggle1() {
        if (document.getElementById('gif-1').style.display == "none") {
            document.getElementById('gif-1').src = '';
            document.getElementById('gif-1').src = 'http://insightgraphicdesign.net/wp-content/uploads/2014/07/coke-responsive-logo.gif';
            document.getElementById('gif-1').style.display = "block";
        } else
            document.getElementById('gif-1').style.display = "none";
    }

    function toggle2() {
        if (document.getElementById('gif-2').style.display == "none") {
            document.getElementById('gif-2').src = '';
            document.getElementById('gif-2').src = 'http://insightgraphicdesign.net/wp-content/uploads/2014/07/coke-responsive-logo.gif';
            document.getElementById('gif-2').style.display = "block";
        } else
            document.getElementById('gif-2').style.display = "none";
    }
</script>

But if I use one gif image it is working properly, see this plunker (sometimes it is not working may be plunker blocking due to security. better put it in a html and check)

2) https://plnkr.co/edit/74huqUZmkoc6T6BdNOlz?p=preview

    <script>
    var img1 = document.getElementById("img1");

    function toggle1() {
        if (document.getElementById('gif-1').style.display == "none") {
            document.getElementById('gif-1').src = '';
            document.getElementById('gif-1').src = 'http://insightgraphicdesign.net/wp-content/uploads/2014/07/coke-responsive-logo.gif';
            document.getElementById('gif-1').style.display = "block";
        } else
            document.getElementById('gif-1').style.display = "none";
    }

</script>

can anyone help me to make the plunker 1 to work? (both gif images should reload whenever I click the two buttons).

Thanks, HariKrishnan P