replaceAll flag not working for lists

The replaceAll flag for updating specific items in a machine list is broken. Is this a known problem?

We need to update a specific credit card record within a credit card list of a customer. We're updating the customer record using WS, where we set the replaceAll flag to false, and provide the specific credit card record that needs to be updated, including the internal id of the credit card. The update succeeds; however, all the other credit cards in the list get wiped out. This exact same behavior can be found when updating addresses as well.

We're using the above to update a list of credit cards on a web store. We cannot use the replaceAll=true to replace the entire list of credit cards every time, since this list cannot be provided every time for the update given that the credit card numbers are masked when retrieved. If you try to write back the credit card records that were retrieved, you get an invalid credit card number error.