2918035 - IQ server becomes unresponsive intermittently, issue more likely to occur after applying 16.1 SP04 PL03 -SAP IQ

IQ server becomes unresponsive intermittently with following message in .srvlog/.stderr.
It can be seen with or without an IQ upgrade.
However, the issue is more likely to occur after upgrading from 16.1 SP02 PL17 to 16.1 SP04 PL03.

 => "Task 144a16870(Request task 467) is trying get forbid mutex held by task 14569a5b0(Request task 474) for more than 60000 ms"

According to customer, problem symptoms are like below,

• cpu usage is 0 % during the issue
• no connection is allowed during the issue
• persists symptom for about 1 ~ 2 minutes once the issue occurs
• lot's of jobs are canceled during the issue

Suspect stacks ,

---------- tid# ..... ----------
.. timestampnow(??) + 0x14
.. a_db_message::set_text( ...
.. a_db_message::a_db_message( ,..
...
.. DBMsgList::AddMessage ...
...
.. MessageDispatcher::Send( ..
...
.. ForbidMutexSet::get(unsigned int) ..
...
.. Worker::get_forbid_mutex(..
..

• SAP IQ16.1 SP04.03
• SAP HANA Dynamic Tiering 2.0 Rev 47

'get forbid mutex' , 'Cancellation request received' , 'ForbidMutexSet::get' , 'ForbidMutexSet' , , KBA , BC-SYB-IQ , Sybase IQ , Bug Filed