Adding bank account to Supplier

Currently trying to create a new supplier and add the supplier bank account details.

1. The customer codes does not exist and is able to be saved / created, without adding a bank account

2. When adding a bank account ( note that bank account exists in ODSC account) with a unique account code and Branch number, the below error occurs. This stops the transaction from being saved.

'This entry already exists in the following tables 'BP-Bank account' (OCRB) (ODBC-2035) [message 131-183]

Please help.