Unable to tag same bank accounts with different person

The HDL ExternalBankAccount is failing due to below error. After analysis, it was found that the Same account number already tagged with another person.
"You can't update this record because the SourceSystemId and SourceSystemOwner are invalid."

As discussed with client, they wanted it to be handled as a warning and not as an error, because it’s quite well possible that 2 employees (e.g. a couple) have the same bank account.

Could you please help with the details.