I got this problem after full data was loaded into 0PS_C04 infoCube. As usually it was done by process chain. Process chain returned no errors and all processes ended successfully.
All WBS elements were in tcode LISTCUBE infoCube 0PS_C04 but some of them didn’t have project and company code assigned. As a result of this, reports didn’t show WBS elements and calculations were wrong. In SAP PS side everything seemed normal and correct.
Delete infoCube 0PS_C04 and dimensional table’s data then load WBS elements master data and run process chain to load full data.