Communication fails between from Task Engine to Process Engine

I have the following problem: I have a simple process with a task. The task gets called, data is correctly transfered, then a user works with the task and commits the form. No errors, but the process is not executing from this point on. Problem is that the task’s status is set to “Started” in the Process Instance view, but opening the tasks shows that it’s status is “Completed”. So on the one hand I have a started task in the process, on the other hand i have a completed task. It seems to me that the task engine is not reporting back to the process engine that the task has been finished.
I read in one thread to install TE_7-1-1_Fix4. I have done that too, but still my task is showing started state only. The worry is that when I am using normal broker document the task is completed succcesfully and joining the process, if I try with the JMS message then only I face this problem.

Can someone give me a hint?

How are you completing the task ? Can you make sure if there are no dead condition in your project after task is completed ?

Which version of IS/Broker are you using.
I can see there is some fix regarding JMS messaging :

WTN-1331(MWS_8.0_SP2_Fix3) A task expiration event fails to execute. When using an Oracle database, My webMethods Server JMS messaging services fail to deliver messages send to queues. This leads to task schedule events not being created. This issue is now resolved