INVOICE m8 321

Hi Masters .

My scenarie SRM/SUS Invoices .

ECC 6.0

SAP_APPL 605 SP14

the vendor send Invoices where into one Invoice has some items with same Po and same  Item number.

Example.

PO ... 450000023  item number 10

QTY ORD 20

the confirmation or reception example two partial  example 10 each one  they are processed on Invoice number  126768...  So far, so good

the invoice come to ECC on IDOC and they are proccessed with IDOC_INPUT_INVOIC_MRM  function send the error M8 321

an idea of how to handle this error ?

Thanks on Advanced.