Could you check the following references, they kind of refer to the similar issues:
https://communities.ca.com/thread/99739680
https://communities.ca.com/thread/101473726
XOG of financial transaction
The following type generally corrects ->
externalSource="ORACLE-FINANCIAL" objectType="transaction"
Example:
<?xml version="1.0" encoding="UTF-8"?>
<NikuDataBus xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../xsd/nikuxog_inboundTransaction.xsd">
<Header action="write" externalSource="ORACLE-FINANCIAL" objectType="transaction" version="6.0.11"/>
<Transactions>
<Transaction actualCostRate="10099" actualCostRateCurrency="USD" billRate="10" billRateCurrency="USD"
chargeCode="Scoping" externalID="12348" groupId="12345" importStatus="N" inputTypeCode="Billable"
poNumber="2222" projectID="PD1002" resourceID="aaronBennett" taskID="5023004"
transactionDate="2018-07-15" transactionType="L" units="1" voucherNumber="2345"/>
</Transactions>
</NikuDataBus>