Hi,

It's not a bug. Someone hid the day dropdown for the agenda view. By default it should be visible.

Anyway, I understand your problem and perhaps it is indeed good idea to reset the day to 1 so here's a hook that does this:

add_action('wp_footer', function () {
    if (!wp_script_is('stec-js')) {
        return;
    }
    ?>
    <script type="text/javascript">
        (function($) {
            $(function() {
                $.stecExtend(function(m) {
                    m.$instance.$top.find('.stec-top-menu-date-dropdown')
                        .on(m.helper.clickHandle(), 'ul li', function() {
                            if (m.glob.options.view === 'agenda') {
                                m.glob.options.day = 1;
                            }
                        });
                });
            });
        })(window.jQuery);
    </script>
<?php
});