Pagination on Custom Post Types filtered Archive Page not working correctly (jumps to the first Post)

This is my Custom Post Type "newyork":

add_action( 'init', 'create_post_type' );

function create_post_type() {
    register_post_type( 'newyork',
        array(
            'labels' => array(
            'name' => __( 'New York' ),
            'singular_name' => __( 'New York' )),
            'public' => true,
            'has_archive' => true,
            'query_var' => true,
            'supports' => array( 'title', 'editor', 'revisions', 'thumbnail',),
            'rewrite' => array('slug' => 'newyork')
    )
    );
}

For this i've created an archive-page called "archive-newyork.php" with the "standard" loop:

<?php if (have_posts()) : ?>
                <?php while (have_posts()) : the_post(); ?>
                <div class="post">
                    <h3><?php the_title(); ?></h3>
                </div><!-- .post -->
                <?php endwhile; ?>
                <?php endif; ?> 
                <div id="pagination">
                <?php  if(function_exists('wp_pagenavi')) { wp_pagenavi();} 
                            else { ?>
                                <?php previous_posts_link(__('<div id="left">vorherige Seite</div>')) ?><?php next_posts_link(__('<div id="right">nächste Seite</div>')) ?>
                         <?php }  ?>
                </div>
                <?php wp_reset_query(); ?>

On top of that page i've got a dropdown to filter posts by month:

<select name="archive-dropdown" class="orderby" onchange="document.location.href=this.options[this.selectedIndex].value;">

                    <option value=""><?php _e( 'Bitte den gewünschten Monat auswählen', 'baumwollboerse' ); ?></option>
                    <?php add_filter( 'get_archives_link', 'get_archives_events_link', 10, 2 );
                    wp_get_archives( array( 'post_type' => 'newyork', 'type' => 'monthly', 'format' => 'option', 'show_post_count' => 1 ) );
                    remove_filter( 'get_archives_link', 'get_archives_events_link', 10, 2 ); ?>

                </select>

This works good so far but when i filter, for example, by the month "september 2014" it gives me the 10 posts (as defined on the WP settings page) as expected. …but when i click on "next posts" the page "/newyork/2014/09/page/2/" jumps autpmatically to the first post ever created from that custom post type...

This problem only appears on the filtered month-page. It works perfectly on the unfiltered archive page...

I already "flushed" the rewrite rules by saving/visiting the permalinks page multiple times with no luck!

Any ideas?

Thanks in advance... Jochen