get_value_external() prints item->key_orig (and calls it a "key") despite it is then processing item->key:

zabbix_log(LOG_LEVEL_DEBUG, "In %s() key:'%s'", __function_name, item->key_orig);
...
if (SUCCEED != parse_item_key(item->key, &request))

It would be more useful to see item->key in the logs (or both item->key_orig and item->key).