Nada. Ningun "error description" en el archivo queries.
Encontré esta línea, que corresponde a la edicion del item 603 (con el que estoy haciendo las pruebas). Al parecer, la info si que se "envía" a la DB:
SELECT COUNT(*) AS numrows
FROM (oc_t_plugin_category)
WHERE fk_i_category_id = '34'
AND s_plugin_name = 'cars_plugin'
--------------------------------------------------
0.00024700164794922
**************************************************
UPDATE oc_t_item_car_attr SET i_year = NULL, i_doors = '', i_seats = '', i_mileage = NULL, i_engine_size = NULL, i_num_airbags = '', e_transmission = 'MANUAL', e_fuel = 'DIESEL', e_seller = 'DEALER', b_warranty = 0, b_new = 0, i_power = NULL, e_power_unit = '', i_gears = '', fk_i_make_id = '1', fk_i_model_id = NULL, fk_vehicle_type_id = 1 WHERE fk_i_item_id = '603'