Solution : https://service.sap.com/sap/support/notes/633883 (SAP Service marketplace login required)
Key words : 
system issues error message ke081, completely generated operating concerns, operating concern xy, operating concerns, program error, system converts, operating concern, drilldown reporting, -pa reports, transaction kemo
Related Notes : 
       
| 621048 | Drilldown reporting: EKE081 with reports conversion | 
| 551344 | Unicode Conversion Documentation |