Displaying other pins on a map

Hi

I am trying to display other pins in a map output, but this doesn't seem to be working, how can I do it?

function custom_map_shortcode( $atts ) {
	$atts = shortcode_atts(
		array(
			'id'        => 'maps_location',
			'object_id' => get_queried_object_id(),
		),
		$atts
	);

	if ( ! $atts['id'] || ! $atts['object_id'] ) {
		return 'Field ID and post context are required.';
	}

	$main_location = rwmb_meta( $atts['id'], '', $atts['object_id'] );
	if ( empty( $main_location ) ) {
		return 'No primary map data found.';
	}

	$extra_pins = array(
		array(
			'latitude'   => 53.46565740326415,
			'longitude'  => -2.2326974824510635,
			'title'      => 'University of Manchester',
			'content'    => '<strong>Manchester</strong><br>Premier university.',
			'icon'       => '/wp-content/uploads/2025/03/Map-Pin-Small-2.svg',
		),
		array(
			'latitude'   => -33.920,
			'longitude'  => 18.423,
			'title'      => 'Cape Peninsula University of Technology',
			'content'    => 'CPUT Campus',
			'icon'       => '',
		),
	);

	$map_args = array(
		'width'       => '100%',
		'height'      => '480px',
		'zoom'        => 13,
		'marker'      => true,
		'marker_icon' => '/wp-content/uploads/2025/03/Map-Pin-Small-2.svg',
		'js_options'  => array(
			'mapTypeId'            => 'HYBRID',
			'zoomControl'          => true,
			'zoomControlPosition'  => 'topright',
			'markers'              => array(), // Initialise empty markers array
		),
	);

	// Add extra pins
	foreach ( $extra_pins as $pin ) {
		$map_args['js_options']['markers'][] = array(
			'latitude'   => $pin['latitude'],
			'longitude'  => $pin['longitude'],
			'title'      => $pin['title'],
			'infoWindow' => $pin['content'],
			'markerIcon' => $pin['icon'],
		);
	}

	ob_start();
	rwmb_the_value( $atts['id'], $map_args, $atts['object_id'] );
	return ob_get_clean();
}
add_shortcode( 'custom_map', 'custom_map_shortcode' );

Demo site: https://aidanv14.sg-host.com/property/osborne-road-accommodation-3/