AIF Service don't retrieve table on XML

for a project I need to change the AIF service called “SalesSalesEInvoice”. In particular, I need to retrieve the CustPaymModeTable on the result XML.
In the query used by the service, this table is present and is joined with CustTrans (relationship based on PaymMode field).
We debugged the service execution and we’ve observed that the table is not retrieved because it is not linked via surrogate key (AifSecurityInference.inferField()).
Did you ever had (and solved) that problem?
How can we force the recovery of the table when the join is not based on recid?