I suggested it would be brave to walk away without raising any paperwork. Its always possible that the captain/crew see something differently from the groundcrew and yes, the crew will always take their lead from their captain and nothing can physically stop him and them from walking away. However, he should discuss his concerns with the AGE in the first instance and, if not convinced, he must then raise a maintenance work order. If he doesn't do that, he must expect to explain to his commander why he chose not to raise an entry in the maintenance document and/or why he decided, off his own bat, that he knows better than the engineers what is acceptable and what is not.