Shortcode to display custom field of custom post type works only in some post types

Shortcode to display custom field of custom post type works only in some
post types

I created a shortcode to pull custom fields from a custom post type called
"room", by the post slug. The shortcode works fine within a different
custom post type, but doesn't return anything when used in the same custom
post type (room), or in normal posts/pages.
Interestingly, the fields for "title" and "link" display fine for all post
types. So, I believe the problem must be with my get_post_meta line.
If anyone could help me, I'd really appreciate it.
// Add shortcode for getting specific custom field from custom post type
add_shortcode('room-info', 'room_info_func');
function room_info_func($atts) {
extract(shortcode_atts(array(
'name' => null, 'field' => null,
), $atts));
$excerpt_post_name = $name;
$excerpt_field = $field;
// Get post ID from post slug
$args=array(
'name' => $excerpt_post_name,
'post_type' => 'room',
'post_status' => 'publish',
'showposts' => 1,
'caller_get_posts'=> 1
);
$my_posts = get_posts($args);
$excerpt_out = null; // Return empty if there's no post by that slug
if( $my_posts ) {
$id=$my_posts[0]->ID;
// Get custom field from post ID
$excerpt_out = get_post_meta($id, 'wpcf-'.$excerpt_field, $single=true);
}
switch ($field) {
case 'link': return $res=get_post_permalink($id); break;
case 'title': return $res=get_the_title($id); break;
case 'image-url': return
$res=wp_get_attachment_url(get_post_thumbnail_id($id)); break;
default: return $res="$excerpt_out"; break;
}
}