Solution : https://service.sap.com/sap/support/notes/485155 (SAP Service marketplace login required)
Key words : 
shortened fiscal year, terms drilldown reporting, account correctly, displayed/selected, variable period 1, variable reason, program error, releases > release 4, source code, prerequisites
Related Notes : 
       
| 672255 | Shortened fiscal year/changing fiscal periods | 
| 514251 | "KEYID_NOT_EXIST" calc. w/ spec. periods acc. to Note 485155 | 
| 198834 | Drilldown reportng: FGV003 for currency translation |