Custom post_type with meta_key sticky conflict

I registered a post type called issue and added some meta fields. One of them is the meta_box sticky.

function sticky	(){
  global $post;
  $custom = get_post_custom($post->ID);
  $sticky = $custom["sticky"][0];
  ?>
  <input type="checkbox" id="sticky" name="sticky" value="yes" <?php echo ($sticky == 'yes') ? 'checked="checked"':''; ?>/> <label for="sticky">Check to stick to the frontpage.</label><br />
  <?php } ?>

Well this helps me to get all sticky marked posts and custom posts for a featured slider. The loop:

$wpcust = new WP_Query(
		array(
            'post_type' => array(
                'post',
                'issue',
            ),
			'meta_key'=>'sticky',
			'meta_value'=> 'yes',
			'post_status' => 'publish',
            'showposts' => '2' )
        );
        if ( $wpcust->have_posts() ):
            while( $wpcust->have_posts() ) : $wpcust->the_post();

When I mark a (normal) post sticky it will add all the custom fields for the custom post_type to that post and a I cannot delete them anymore.

Any suggestions?

The whole meta boxing:

add_action("admin_init", "admin_init");

function admin_init(){
  add_meta_box("issue_download", "Download Link", "issue_download", "issues", "side", "low");
  add_meta_box("issue_cover", "Cover Thumb", "issue_cover", "issues", "side", "low");
  add_meta_box("issue_highlight", "Highlight Issue", "issue_highlight", "issues", "side", "low");
  add_meta_box("sticky", "Sticky", "sticky", "issues", "side", "low");
  add_meta_box("issue_meta", "Credits", "issue_meta", "issues", "normal", "low");
  add_meta_box("sticky", "Sticky", "sticky", "videos", "side", "low");

}

function issue_download(){
  global $post;
  $custom = get_post_custom($post->ID);
  $issue_download = $custom["issue_download"][0];
  ?>
  <label>URL:</label>
  <input name="issue_download" value="<?php echo $issue_download; ?>" />
  <?php
}

function issue_cover(){
  global $post;
  $custom = get_post_custom($post->ID);
  $issue_cover = $custom["issue_cover"][0];
  ?>
  <label>URL:</label>
  <input name="issue_cover" value="<?php echo $issue_cover; ?>" /><br />
  <p>Needs to be 320x417px</p>
  <?php
}

function sticky	(){
  global $post;
  $custom = get_post_custom($post->ID);
  $sticky = $custom["sticky"][0];
  ?>
  <input type="checkbox" id="sticky" name="sticky" value="yes" <?php echo ($sticky == 'yes') ? 'checked="checked"':''; ?>/> <label for="sticky">Check to stick to the frontpage.</label><br />
  <?php
}

function issue_highlight (){
  global $post;
  $custom = get_post_custom($post->ID);
  $issue_highlight = $custom["issue_highlight"][0];
  ?>
  <input type="checkbox" id="issue_highlight" name="issue_highlight" value="highlight" <?php echo ($issue_highlight == 'highlight') ? 'checked="checked"':''; ?>/> <label for="issue_highlight">Check to make cover alpha 100%</label><br />
  <?php
}

function issue_meta() {
  global $post;
  $custom = get_post_custom($post->ID);
  $issue_meta = $custom["issue_meta"][0];
  ?>
  <p><textarea cols="50" rows="15" name="issue_meta"><?php echo $issue_meta; ?></textarea><br />
  This content is shown on the right side and could include the table of content, credits or other meta information of the issue.</p>
  <?php
}

add_action('save_post', 'save_details');

function save_details(){
  global $post;

  update_post_meta($post->ID, "issue_download", $_POST["issue_download"]);
  update_post_meta($post->ID, "issue_cover", $_POST["issue_cover"]);
  update_post_meta($post->ID, "sticky", $_POST["sticky"]);
  update_post_meta($post->ID, "issue_highlight", $_POST["issue_highlight"]);
  update_post_meta($post->ID, "issue_meta", $_POST["issue_meta"]);
}