Solution : https://service.sap.com/sap/support/notes/935656 (SAP Service marketplace login required)
Key words : 
sapbwnews bw support package 17 netweaver'04 stack 17, n_enq_loop_count   static attribute   type i2, n_enq_dump_failed   static attribute   type rs_boolb, 10 content            import support package 25, 0b            import support package 31, 50            import support package 17, 1 content support package 25, long queue times, sequential processing reason, 0b support package 31
Related Notes : 
       
| 1107434 | OLAP cache consultation: Long wait times due to locks | 
| 982402 | Import_Container_Missing and cache entries w/o buffer ID | 
| 969194 | Inconsistencies: BI SP and BIA revision are incompatible | 
| 949151 | Deleted selections in the cache are still used in OLAP | 
| 921951 | Format error with IMPORT: No other container found | 
| 898545 | OLAP cache, entries disappear | 
| 898418 | OLAP cache - terminations during the reading | 
| 872277 | SAPBWNews BW Support Package 17 NW'04 Stack 17 RIN | 
| 872274 | SAPBWNews BW 3.1 Content Support Package 25 | 
| 872272 | SAPBWNews BW 3.0B Support Package 31 | 
| 860013 | Query cannot use cache -missing query name in cache | 
| 790859 | Dump with OLAP cache with file access due to netwk problems | 
| 751402 | Cache use: Can change queries w/ variables during navigation |