Order Extension working only on first line added

Summary: Hi Team,

We are trying to default few fields via Order extension, the reason why we did not choose pretransformation is, it doesn't work on copied order

The issue with order extension is, all fields works perfectly except Schedule Ship date (With Override Flag as 'Y') and Receivable Transaction

Actual Issue:

When we create multiple lines in an order, it works only on the first line for Schedule Ship date and Receivable Transaction. Screenshot attached

Code used:

import oracle.apps.scm.doo.common.extensions.ValidationException;
import oracle.apps.scm.doo.common.extensions.Message;

String VarOrderType = header.getAttribute ("TransactionTypeCode");
def BUName= header.getAttribute("BusinessUnitName");