Custom action not fired properly

I've made this custom action that updates a cck field value on the db.

function miocsv_setexported_action(&$object, $context = array()) {
[...]

  if ($nid) {
    $data = new stdClass();
    $data->nid = $nid;
    $data->field_flag_esportato_value = 1;

    drupal_write_record('content_type_scheda', $data, array('nid'));
    content_clear_type_cache();
    // record a message noting the action taken
    watchdog('action', 'Esportata la scheda  %title', array('%title' => $title, '%nid' => $nid));
    break;
  }
}

Later I've created a field_button that fires this custom action using a rule.
It updates the field on the db only if I leave the break; line, thus forbidding to fire another action in the same rule.
When debugging with firebug I see an error that says "Fatal error: Cannot break/continue 1 level in ... miocsv.module", apparently related to json_encode.
If I take off the break; line or replace with a return false; one the field on the db is no more updated, even though drupal_write_record() returns SAVED_UPDATED value.