3397012 - Get error message Q3221 "Code *** is being used and cannot be delete" when trying to delete a code in a code group

You are trying to delete a code in a code group in Edit Code Groups app. However, you get the error message Q3221 "Code *** is being used and cannot be delete".
Usually, the "Usage Indicator" is ticked for the code and you can see that it is used in some selected sets in the "Where-Used List". However, even after you have deleted them in the corresponding selected set, the same error still happens.

SAP S/4HANA Cloud, public edition, CE2308

QS3221, Edit Code Groups. selected set, Usage Indicator, code group , KBA , QM-PT-BD-CAT-2CL , Catalog (Public Cloud) , Problem