3555992 - IQ16.1 SP05.09 appears to hang during BACKUP - SAP IQ

Backup seems to hang during checkpoint

------------ Sample from iqmsg
I. 11/04 07:13:22. 0000009185 [20949]: Number of IQ blocks backed up: 2050000 
I. 11/04 07:13:25. 0000009610 IQ Checkpoint position: 0
I. 11/04 07:13:26. 0000009610 Chk
I. 11/04 07:13:26. 0000009610 ChkDone [NumTxnCP: 1]
I. 11/04 07:13:26. 0000009610 IQ Checkpoint block: 6594
I. 11/04 07:13:26. 0000009610 PostChk  <-----
I. 11/04 11:55:06. 0000000000 IQ OpenDatabase, checkpointblock: 6594, recover: 1
------------

Stack trace during such hang shows following problem thread

------------ Problem thread ------
pc: 0x400e81 <unknown>
pc: 0x7fe00685cef4 pcstkwalk()
pc: 0x7fe00685d620 ucstkgentrace()
pc: 0x7fe6000a3910 <unknown>
pc: 0x7fe60009e70c <unknown>
pc: 0x7fe0065f463d hos_condvar::Wait()
pc: 0x7fe006851ae1 hos_team::StartWork()
pc: 0x7fe006832d41 hos_team::Exec()
pc: 0x7fe007503b30 db_IQbackup::Execute()
pc: 0x7fe007530289 db_DoBackup::Execute()
pc: 0x7fe0073f0e07 st_command::DoCmdThroughResourceGate()
pc: 0x7fe007438045 st_iqctl::DoBackupRestore()
pc: 0x7fe00613ee24 UIQCtl_DoBackupRestore
pc: 0x7fe0074417cb st_SAIQInterfaceInfo::callFunction()
pc: 0x7fe0074a7a4e st_SAIQInterface::RunIQFunc()
pc: 0x7fe007441c8b st_SAIQInterface::Execute()
pc: 0x7fe00686d8bb saint_iqthresholdctl::DoBackupRestore()
pc: 0x7fe6006941ba ArchiveBackup()
pc: 0x7fe6006954bd dbi_backup_database()
pc: 0x7fe6006ec9c9 DoExecuteBodyLocal()
pc: 0x7fe6006eda15 DoExecuteStmt()
pc: 0x7fe60062ddf2 exec_procedure_stmt()
pc: 0x7fe6006301f0 run_procedure()
pc: 0x7fe6006316f7 call_procedure()
pc: 0x7fe600633e8d DB_Exec_event_handler()
pc: 0x7fe6004b954b EventHandler::do_request()

------------

IQ 16.1 sp05.09

CR 830202, 830202, CR830202, CR#830202 , KBA , BC-SYB-IQ , Sybase IQ , Problem