Thank you for your replies.
you are all right, we should have kept our samples for longer.
we are trying to recall parts of the same batch from another customer. (we have provided another customer from the same batch and they had no complain about the product).
meanwhile, just to help me learn...
we produce brass rods and recently have received a quality complaint from a forging customer.
we have delivered two different batches to the customer. the customer is satisfied with the first batch, while complains about the second batch.
the chemical composition of both batches are similar...
