Meta Box

Hello, I'm also having an issue with select_advanced that seems to be different from the above. My metabox settings are:

array(
    'name'  => 'Guests',
    'id'    => $prefix . 'sessionguests',
    'type'  => 'post',
    'post_type' => 'guests',
    'field_type' => 'select_advanced',
    'multiple' => true,
    'placeholder' => 'Who are the guests?',
),

But when I try to populate the field in a post, it attempts to make an AJAX call but returns "The results could not be loaded." There's a Javascript error that says "[Error] Failed to load resource: the server responded with a status of 400 (Bad Request) (admin-ajax.php, line 0) http://localhost:8888/wp-admin/admin-ajax.php?_type=query"

I can confirm that changing field_type to "select" works, but this is not a good option for me because of the large number of possible guests. I don't have The Event Calendar plugin, which I saw in another thread caused a conflict. Any other suggestions?

I am having the same problem. Here are my fields:

add_filter( 'rwmb_meta_boxes', 'aka_register_taxonomy_meta_boxes' );
function aka_register_taxonomy_meta_boxes( $meta_boxes )
{
	$meta_boxes[] = array(
		'title'      => 'Guest Category Fields',
		'taxonomies' => 'guestcats',
		'fields' => array(
			array(
				'name' => 'Featured image',
				'id'   => 'guestcatimage',
				'type' => 'image_advanced',
				'max_file_uploads' => 1,
			),
			array(
				'name' => 'Include in ‘Guests by Fandom’ pulldown?',
				'id'   => 'guestbyfandom',
				'type' => 'checkbox',
			),
		),
	);
	return $meta_boxes;
}

Some of the categories work as expected, but others will not save either the checkbox or the image. What's stranger is: when it fails to save an image to one of the terms, that image gets saved to one of the other terms that had been working. I have WP debug enabled and don't see any errors. Any suggestions?