Customer Bank Account Primary Owner not creating through FBDI

Summary:

When loading Customers through the CustomerImportTemplate FBDI, the Primary Owner and additional Joint Owners of the Bank Account are not being added to the Bank Account record. The Bank Account is being created, however no Owners are being assigned.

How can we assign the Bank Account Primary and Joint Owners through the FBDI upload? There is a 'Y/N' option for Primary Owner that we have tried using, but this does not assign any Owners.