Solution : https://service.sap.com/sap/support/notes/697884 (SAP Service marketplace login required)
Key words : 
//sapserv3/general/r3server/abap/note, smqr inbound scheduler remains, lowest queue count, relevant support package, all_queues internal table, corrected wx4k001287 transport, corrected gdlk000315 transport, inbound ready reason, inbound scheduler, internal table
Related Notes : 
       
| 744869 | Optimizing the performance of inbound scheduler | 
| 481278 | Installing qRFC Version 6.20.045 | 
| 438015 | Latest qRFC version and supplement for 3.x, 4.x, 6.10, 6.20 |