How to use Source Location constraint in Customer Account Number

Summary:

I would like to pass my account number to a service provider connected via an External Rating Engine. The "Shipment Customer Account Number" RBI is available.

For the service provider in question we have multiple account numbers based on our source locations.

Content (please ensure you mask any confidential information):

When including it in the fieldset and creating a Customer Account Number with just the Service Provider GID the account number is present in the XML to the ERE. However, when adding a source location restriction to the Customer Account Number based on either

a) the source location of the Order Release OR