Bootstrap 3, data-show not working

If data-show="true", then when you call $('.modal').modal(), the modal shows up. But if data-show="false", $('.modal').modal() doesn't work, you need to call $('.modal').modal('show') instead.

It's actually not a bug because the documentation says:

Shows the modal when initialized.

Therefore you need to initialize your Modal "manually" by JS:

<script type="text/javascript">
    $( function(){
        $('#myModal').modal();
    } )
</script>