Solution : https://service.sap.com/sap/support/notes/1668991 (SAP Service marketplace login required)
Key words : 
detect commutative formula parts automatically, commutative formula parts, related notes section, rsadmin-parameter faggr_before, terms bw730 optimizations, formula exception aggregation, calculated key figure, table rsadmin, faggr_before reason, object 'faggr_before'
Related Notes : 
       
| 1724829 | Error in CL_RSR_RRI2_FAGGR and form _GET_LS_NEW-01- | 
| 1722195 | Unable to generate query due to missing secondary key | 
| 1712991 | Formula before aggregation, lookup, and FAGGR_BEFORE | 
| 1673704 | Query including count on key figure fails to generate | 
| 1669100 | Query fails to generate with error GET_RELATIV_FEMS | 
| 1666557 | query generation fails with error 'BIT_OFFSET_NOT_POSITIVE' | 
| 1662221 | Error in SAPLRRI2, form LRECH_E_FUELLEN-01- / incorrect data | 
| 1658551 | Query with Currency/Unit Conversion does not generate | 
| 1656819 | query generation fails with short dump GET_CHANM-01- | 
| 1655115 | Incorrect or no data for formula exception aggregation | 
| 1648222 | Long runtime during query generation and query check | 
| 1646122 | Long runtime for query generation | 
| 1645362 | Generation error when using a query as an InfoProvider | 
| 1639260 | large query does not generate successfully | 
| 1636053 | Upgrade to SAP NetWeaver 7.30: BW server: Useful SAP Notes | 
| 1634124 | query generation fails after BW730 SP03 | 
| 1628615 | Query generation terminates for key figures that have units | 
| 1622657 | Query generation terminates in SET_CUMORE | 
| 1618853 | X299 Brain in CL_RSR_RRI2_LRECH; _AJUST_LRECH_AGGR_02-02- | 
| 1607355 | X299 Brain in SAPLRRI2, form LRECH_F_FUELLEN-05- | 
| 1599805 | X299 Brain in the class CL_RSR, method GET_CHANM-01- | 
| 1587629 | Subsequent correction to Note 1583950 | 
| 1573569 | Runtime error in query generation GETWA_NOT_ASSIGNED | 
| 1467200 | Subsequent correction for Note 1464540 |