Production version cannot be deleted as RP quantities exist

What causes this issue?

You want to delete a production version. However, actual quantities
(WIP quantities) still exist for this production version in the current
period. You cannot delete the production version until all actual
quantities have been reduced.

System Response

The production version cannot be deleted.

How to fix this error?

Before you can delete the production version, you must reduce the
existing actual quantities.

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.