I haven’t figured out why WordPress is missing schedule post, but I wrote a script that is ran with crontab that notifies me when it happens.

<?php

include 'wp-load.php';

$total_missed_schedules = 0;

$blogs = crontab_get_blogs();

$output = '';

foreach($blogs as $blog) {
	$blog_prefix = $wpdb->get_blog_prefix( $blog->blog_id );

	$results = query_missed_schedules( $blog_prefix );

	$total_missed_schedules += count($results);

	$output .= ($blog->domain . ' (blog id:' . $blog->blog_id . ') missed schedules ' . count($results) . '<br />' . PHP_EOL);

	if ($results) {

		switch_to_blog( $blog->blog_id );

		foreach ( $results as $row ) {
			$output .= ("post_id: <a href='" . get_edit_post_link($row->ID) . "'>" . $row->ID . "</a> date: " . $row->post_date . " post_type: " . $row->post_type . "<br />" . PHP_EOL);
		}

		restore_current_blog();
	}
}

echo $output;

if ($total_missed_schedules > 0 || isset($_GET['mailtest'])) {

	$to = 'matt@thiessen.us';
	$subject = 'Missed scheduled posts';
	$text = '';

	if(isset($_GET['cron_src'])) {
		$text = 'cron ran from ' . $_GET['cron_src'];
		$text .= '<br />wget http://thegazette.com/missed_pub_notifier.php<br /><br />';
	}

	add_filter('wp_mail_content_type',create_function('', 'return "text/html";'));
	wp_mail($to, $subject . " (wp_mail)", $text . $output);
}

function query_missed_schedules( $blog_prefix ) {
	global $wpdb;

	$sql = "SELECT ID, post_date, post_date_gmt, post_type, post_title FROM " . $blog_prefix . "posts WHERE post_status = 'future' AND post_date_gmt <= UTC_TIMESTAMP();";

	$results = $wpdb->get_results($sql);

	return $results;
}

function crontab_get_blogs() {
	global $wpdb;

	$sql = "SELECT blog_id, domain, path FROM $wpdb->blogs WHERE deleted = 0 AND archived = '0' ORDER BY domain, path";
	$results = $wpdb->get_results($sql);
	return ($results);
}

?>

Display login or register link

<?php if(is_user_logged_in()):?>

<?php else: // not logged in ?>
<?php wp_die('Sorry, you must first '. wp_loginout( get_permalink() ).' to view this page. You can '.wp_register( '', '').'.'); ?>
<?php endif; // logged in? ?>

This function from dev4press really helped me debug my custom post type redirect to a 404 page.

Place this code in your functions.php file:

function dev4press_debug_page_request() {
		global $wp, $template;

		echo '<pre>!-- Request: ';
		echo empty($wp->request) ? "None" : esc_html($wp->request);
		echo ' -->'.PHP_EOL;
		echo '!-- Matched Rewrite Rule: ';
		echo empty($wp->matched_rule) ? None : esc_html($wp->matched_rule);
		echo ' -->'.PHP_EOL;
		echo '!-- Matched Rewrite Query: ';
		echo empty($wp->matched_query) ? "None" : esc_html($wp->matched_query);
		echo ' -->'.PHP_EOL;
		echo '!-- Loaded Template: ';
		echo basename($template);
		echo ' --></pre>'.PHP_EOL;
	}

Place this in your template file:

dev4press_debug_page_request();

echo '<h1>Rewrite Rules</h1>';

global $wp_rewrite;

echo '<pre>';
print_r($wp_rewrite->rules);
echo '</pre>';

$custom_posts_caps = array('edit_custom_post',
'read_custom_post',
'delete_custom_post',
'edit_custom_posts',
'edit_others_custom_posts',
'publish_custom_posts',
'read_private_custom_posts');

_smg_add_cap('administrator', $custom_posts_caps);
_smg_add_cap('editor', $custom_posts_caps);

'capabilities' => array(
'edit_post' => 'edit_custom_post',
'read_post' => 'read_custom_post',
'delete_post' => 'delete_custom_post',
'edit_posts' => 'edit_custom_posts',
'edit_others_posts' => 'edit_others_custom_posts',
'publish_posts' => 'publish_custom_posts',
'read_private_posts' => 'read_private_custom_posts'
),

All of this is created in a class

// place this in __construct of the class
$this->nonce_name = 'name_' . $my_post_type_slug;
$this->nonce_action = 'saving_posttype_' . $my_post_type_slug;
add_action('save_post', 'save_my_custom_posttype', 10);

// place this in a meta box
echo '
';

// your custom save w/ nonce
function save_my_custom_posttype($post_id) {

	if (isset($_POST[ $this->nonce_name ]) && wp_verify_nonce( $_POST[ $this->nonce_name ], $this->nonce_action ) !== false ) {
		// do something
	}
}