Error while closing command context 5.9 to 5.11 and above

[nal_raj]

While migrating 5.9 to 5.11 and above, but its working fine for 5.10.
i am getting following error, db url as follows
"jdbc:h2:mem:alm:activiti;DB_CLOSE_DELAY=-1"
Or
"jdbc:h2:tcp://localhost/~/activiti;DB_CLOSE_DELAY=-1"

even i have tried with DB_CLOSE_ON_EXIT=FALSE;

Version h2- 1.4.181

Oct 16, 2015 6:13:36 PM org.activiti.engine.impl.interceptor.CommandContext close
SEVERE: Error while closing command context
org.activiti.engine.ActivitiException: Exception while invoking TaskListener: Exception while invoking TaskListener: null
        at org.activiti.engine.impl.persistence.entity.TaskEntity.fireEvent(TaskEntity.java:529)
        at org.activiti.engine.impl.bpmn.behavior.UserTaskActivityBehavior.execute(UserTaskActivityBehavior.java:94)
        at org.activiti.engine.impl.pvm.runtime.AtomicOperationActivityExecute.execute(AtomicOperationActivityExecute.java:44)
        at org.activiti.engine.impl.interceptor.CommandContext.performOperation(CommandContext.java:85)
        at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperationSync(ExecutionEntity.java:535)
        at org.activiti.engine.impl.persistence.entity.ExecutionEntity.performOperation(ExecutionEntity.java:530)
        at org.activiti.engine.impl.pvm.runtime.AtomicOperationTransitionNotifyListenerStart.eventNotificationsCompleted(AtomicOperationTransitionNotifyListenerStart.java:52)

[jbarrez]

I don't believe the database is the issue here.
Is this the same process as in your other posts (eg https://forums.activiti.org/content/exception-while-invoking-tasklistener-null) ?

[nal_raj]

Yeah it's same process..post as follows
http://forums.activiti.org/comment/31632#comment-31632
http://forums.activiti.org/comment/31633#comment-31633
If I summaries. ..taskService.complete(taskID); will make any difference if we make a call from callback(trying to execute three userTask from three process XML by callback)
Needless to say …its working for 5.9 and 5.10 but not 5.18.0.
Please help. ..I have blocked here.