Serial number &1 can no longer be changed

What causes this issue?

You can no longer delete the serial number &v1& from the object list for
inspection lot &v2&, because defects or results have already been
recorded for this serial number.

System Response

You can only delete the serial number, if no defects or single values
are assigned to this serial number in inspection lot &v2&.

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

How to fix this error?

If you want to delete the serial number, you should delete the defects
recorded for this serial number and set the attribute for the single
value to invalid.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.