Meta Box

	//Panelists

	$meta_boxes[] = array(
			'title'      => 'Panelists',
			'context'    => 'normal',
			'priority'   => 'high',
			'post_types' => 'events',
			'desc'       => '(drag to reorder)',
			'fields' 	 => array(
				array(
						'id'         => 'radix_panelists',
						'type'       => 'group',
						'clone'      => true,
						'sort_clone' => true,
						'fields'     => array(
							array(
									'name'  => 'Position',
									'id'    => $prefix . 'panelistposition',
									'type'  => 'text',
									'desc'  => 'Position on panel: e.g. Panelist, or Chair',
							),
							array(
									'name'  => 'Name',
									'id'    => $prefix . 'panelistname',
									'type'  => 'text',
									'desc'  => 'Name of panelist',
							),
							array(
									'name'  => 'Title',
									'id'    => $prefix . 'panelisttitle',
									'type'  => 'text',
									'desc'  => 'Title of panelist',
							),
							array(
									'name'  => 'URL',
									'id'    => $prefix . 'panelisturl',
									'type'  => 'text',
									'desc'  => 'Link or mailto: for panelist',
							),
							array(
									'name'  => 'Profile Pic',
									'id'    => $prefix . 'panelistpic',
									'type'  => 'file_input',
									'desc'  => 'Profile picture of panelist',
							),
					),
				),
			),
	);

Confirmed. The default white space is somehow being saved as a populated field when the post is updated.

I renamed the group and the if !empty worked. I updated a post, leaving these fields blank, and it stopped working.

Even if these fields are left blank, the empty fields still register as being content and if !empty returns true.

I'm gonna use a checkbox to hide this section for now and query that instead.

Full code, if it helps anyone in future (note that I had to adapt it slightly for use with Co-Authors Plus, so it echoes user_login with the prefix cap- and then uses that in the tax_query):

// Return an array of radix_authoraccount, if not empty, for management, board and fellows post types

	$teamargs = array(
		'post_type' => array('management','fellows','board'),
		'posts_per_page' => -1,
	);

	$team_posts = wp_get_recent_posts( $teamargs );

	$theteamauthors = array();

		foreach( $team_posts as $teamauthors ) { 

	 		if (rwmb_meta( 'radix_authorcheckbox', '', $teamauthors['ID']) == 1 ) {

	 			$teamauthorlist = rwmb_meta( 'radix_authoraccount', '', $teamauthors['ID']);

				$getpostauthor = get_user_by( 'id', $teamauthorlist );
				$authorlogin = $getpostauthor->user_login;

	 			$theteamauthors[] = array('cap-' . $authorlogin);

	 		}

	 	}

// Sort array to remove duplicate authors

	// print_r($teamauthorlist);

	$authorarray = array_unique($theteamauthors, SORT_REGULAR);

	$authormap = array_map('array_pop', $authorarray);

	$theauthors = implode(",",$authormap);

	// echo $theauthors;
	
// Run query to retrieve active posts by these authors

	$args = array(
	    'numberposts' => '10',
	    'orderby' => 'post_date',
	    'order' => 'DESC',
	    'post_type' => array( 'post', 'work', 'news' ),
	    'meta_query'     => array(
			array(
				'key'     => 'radix_status',
				'value'   => 'value1',
				'compare' => '==',
				)
		),
		'tax_query' => array(
			array(
				'taxonomy' => 'author',
				'field' => 'slug',
				'terms' => explode(',', $theauthors)
			)
		)
	);

	$recent_posts = new WP_Query ($args);

	if ( $recent_posts->have_posts() ) {

		echo '<div class="teamworklist"><ul>';

		while ( $recent_posts->have_posts() ) {
			$recent_posts->the_post();

			// Post Title

			$title = apply_filters( 'genesis_post_title_text', get_the_title() );
			echo '<li>';
			echo sprintf( '<h1 class="team-work entry-title"><a href="%s" rel="bookmark">%s</a></h1>', get_permalink(), $title );

			// Post Date

			echo get_the_date();
			echo '<br>';

			// Authors

			echo 'By ';

			coauthors_posts_links();

			echo '</li>';

		}

		echo '</ul></div>';

	} else {

	}

Latest update:

I got it returning SOME values, by using:

// Return an array of radix_authoraccount, if not empty, for management, board and fellows post types

	$teamargs = array(
		'post_type' => array('management','fellows','board'),
	);

	$team_posts = wp_get_recent_posts( $teamargs );

	$teamauthorlist = array();

		foreach( $team_posts as $teamauthors ) {  

	 		if ( !empty( array(rwmb_meta( 'radix_authoraccount', '', $teamauthors['ID']) ) ) ) {

	 			$teamauthorlist[] = array(rwmb_meta( 'radix_authoraccount', '', $teamauthors['ID']));

	 		}

	 	}

// Sort array to remove duplicate authors

print_r($teamauthorlist);

$authorarray = array_unique($teamauthorlist, SORT_REGULAR);

$theauthors = array_values( $authorarray );

// print_r($theauthors);'

But the values returned aren't quite right... According to the user data I can see, and the users assigned using radix_authoraccount, I should be getting:

234455678

Instead, the above code is returning:

2333445578

That's two extra 3s and a missing 6... Getting closer, but something's not quite right...

100% correct! Sorry, Anh! Feel like an idiot now! Clearing the cache is usually the first thing I do! XD

Thanks so much for the help!

Completely uninstalled the plugins, downloaded the very latest versions and reinstalled. Seems to have done the trick!