And your header guide is correct? The guide above only an exsample?
In the product struktur you have no item reference to the orderadm_i, this could be a problem.
You have either generate a own guide for you item or use a handle. Try to fill your handle every where with '1'. If you dont do that the system dont know that the product structure is assosiated with the orderadm:i
And delete the ref_guid here, use handle every where.
ls_input_fields-ref_handle = '0000000000'.
ls_input_fields-ref_guid = '514E841100C34430E1008000AC1010B7'.
ls_input_fields-ref_kind = 'A'.
ls_input_fields-objectname = 'ORDERADM_I'.