Function is not possible for completed item(s)

What causes this issue?

The items that have been processed and completed as a quality
notification can no longer be changed in defects recording.

System Response

The selections that you are not allowed to make are cancelled. The
function is carried out for the permissible selections.

How to fix this error?

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.