Hi Ruben,
BAPI_ALM_ORDER_MAINTAIN might not be used for Production orders. This BAPI is used for PM/Servicer orders.
Please see this document Using BAPI_ALM_ORDER_MAINTAIN to update production order component if you still want to use this BAPI.
Also if you already implemented the Enhancement mentiones in documents, than check if the components are non stock items.
Regards,
Amarnath Dube