add_filter( 'wpseo_breadcrumb_single_link', 'bybe_crumb_fix' , 10, 2 );
function bybe_crumb_fix( $output, $crumb ){
  if ( is_array( $crumb ) && $crumb !== array() ) {               
    if( strpos( $output, '<span class="breadcrumb_last"' ) !== false  ||   strpos( $output, '<strong class="breadcrumb_last"' ) !== false ) { 
      $output = '<a property="v:title" rel="v:url" href="'. $crumb['url']. '" >';
      $output.= $crumb['text'];
      $output.= '</a>';
    } else { $output .= "</span>"; }
  }
  return $output;
}