Diagnosis
If the item number increment is too big, this can result in itemnumbers which are not permitted.

System Response
The area for item numbers above 900000 in delivery processing isreserved for special items (batch split and packaging material items).and cannot be used for normal delivery items.

Procedure
Choose the item number increment so that you know that the item numberarea will not be above 900000 for processing your businesstransactions.