Optimization server &1 could not be released

What causes this issue?

Optimization server &V1& could not be released. The administrative
routine could not unlock optimization server &V1& for user &V2&.

System Response

Processing cannot be continued.

How to fix this error?

Exit the transaction.

Procedure for System Administrators

Try to unlock the optimization server manually, by deleting the lock
entry.

Error message extract from SAP system. Copyright SAP SE.