Employee has multiple CSN [BSN] numbers assigned: &1 and &2

What causes this issue?

Employee has multiple CSN [BSN] numbers assigned in the infotype 0002,
but only a unique CSN [BSN] number is allowed.

System Response

The employee is rejected in payroll.

How to fix this error?

Assign the CSN [BSN] number as of the last hire date, maximized to 5
years, and maintain the CSN [BSN] number as of the birthdate.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.