ECC to CRM BP Grouping Mapping / Replication

In our current implementation when a customer record is created in ECC using Tx XD01 account group 0001 sold-to it creates and ECC business partner with the same number and BP Grouping CUBP. It is then replicated to CRM and creates a BP with the same BP record # as ECC but in CRM BP Grouping Z1. After replicating customizing object DNL_CUST_KTOKD for a new account group we are getting a Bdoc error saying that CUBP does not exits for both the new account group as well as 0001. Where or how is the relationship between ECC BP Grouping CUBP to CRM BP Grouping Z1 established / maintained?

Any help is greatly appreciated!

-Kris