credit transaction - transaction type derive logic

Summary:

Hi Team

In our project, client is doing a credit memo of AR invoices which have come from Oracle project contract invoices. ( transaction source is contract invoices)

Which original invoice is SA invoice，and when user try to credit the transaction in AR invoice UI, she manually choose the credit memo's transactioon type is Manual credit memo.

But once it saved, system will auto change the transaction type is SA credit memo, not maually choosed Manual credit memo transaction type.

We are wondering if it's because for SA invoice transaction type setup, we specify the Credit Memo Type is 'SA Credit Memo' ?