Solution : https://service.sap.com/sap/support/notes/154173 (SAP Service marketplace login required)
Key words : 
additional key words raiminfo, drill-downsummarization imc0, symptom plan, actual values, wbs elements, im reporting, cost element, indicator 'suppress', differences occur, ps reporting
Related Notes : 
       
| 152579 | IM reprtng:plan revenues of WBS elmnt were dsplayd | 
| 134621 | IM/PS reporting: Plan/budget/residual plan differ |