More than one taxonomy/taxonomy_advanced field = last instance overrides others

When adding more than one taxonomy or taxonomy_advanced fields to a post/page with different and unique ids, all fields simply save the value of the last one present. In the example below, whatever value is selected for category_feed becomes the saved value for both category_feed and category_feed_short regardless of what is selected for category_feed_short. How do I add multiple category select fields with ability to save a different selection for each?

function stories_custom_fields($meta_boxes) {
  $prefix = 'category_feed_short_';
  $meta_boxes[] = array(
    'id' => 'category_feed_short',
    'title' => 'Article feed by category - Short format',
    'context' => 'normal',
    'priority' => 'default',
    'autosave' => true,
    'post_types' => array('page'),
    'include' => array(
      'template' => array('page-originals-single.php')
    ),
    'fields' => array(
      array(
        'id' => $prefix . 'headline',
        'name' => 'Headline',
        'desc' => 'Default: Find out more',
        'type' => 'text',
      ),
      array(
        'name' => 'Category',
        'id' => $prefix . 'select',
        'type' => 'taxonomy_advanced',
        'taxonomy' => 'category',
        'field_type' => 'select_advanced',
        'multiple' => false
      )
    )
  );

$prefix = 'category_feed_';
  $meta_boxes[] = array(
    'id' => 'category_feed',
    'title' => 'Article feed by category - Article format',
    'context' => 'normal',
    'priority' => 'default',
    'autosave' => true,
    'post_types' => array('page'),
    'include' => array(
      'template' => array('page-originals-single.php')
    ),
    'fields' => array(
      array(
        'id' => $prefix . 'headline',
        'name' => 'Headline',
        'desc' => esc_html__('Default: A deeper look'),
        'type' => 'text',
      ),
      array(
        'name' => 'Category',
        'id' => $prefix . 'select',
        'type' => 'taxonomy_advanced',
        'taxonomy' => 'category',
        'field_type' => 'select_advanced',
        'multiple' => false
      )
    )
  );
  return $meta_boxes;
}

add_filter('rwmb_meta_boxes', 'stories_custom_fields');