Solution : https://service.sap.com/sap/support/notes/885733 (SAP Service marketplace login required)
Key words : 
sapbwnews bw support package 15 netweaver'04 stack 15, rsadmin parameter 'adjust_new' = 'x', 10 content            import support package 23, 0b            import support package 29, 50            import support package 15, 1 content support package 23, 0b support package 29, part provider reason, support package, sapbwnews bw3
Related Notes : 
       
| 887801 | Long runtime in the REMOVE_SELDR_0INFOPROV_NEW form | 
| 836440 | SAPBWNews BW Support Package 15 NW'04 Stack 15 RIN | 
| 825396 | Performance in reports with many selections | 
| 823654 | Long runtimes in the form: adjust_input_for_multicube | 
| 783253 | SAPBWNews BW 3.1 Content Support Package 23 | 
| 783251 | SAPBWNews BW 3.0B Support Package 29 |