on-complete of a default on-error tasks sometimes doesn't run

In a big workflow (~60 tasks) the on-complete of a default on-error tasks sometimes doesn't run.

The workflow is ~700 lines and some of the tasks are nested or call a custom action. The default on-error calls a task (system_task_on_error) that has an on-complete section.

...
  task-defaults:
    on-error:
    - "system_task_on_error"
  tasks:

    system_task_on_error:
      workflow: "my_workflow"
      input:
        env: "<% env() %>"
        workflow_parameter_05: "xyz"
        workflow_parameter_06: "xyz"
      join: 1
      on-complete:
      - "problematic_task"
...

I tried reproducing the issue with a smaller workflow, but it didn't work.

To reproduce download the attached file and:
tar -xf big_wf_on_complete_line_678_not_running_2609.tar.gz
mistral workflow-create big_wf_on_complete_line_678_not_running_2609.yaml
mistral workflow-create my_workflow_2609.yaml
mistral workflow-create failing_workflow_2609.yaml
mistral action-create my_action_2609.yaml
mistral execution-create big_wf_on_complete_line_678_not_running inputs.json params.json

see result of calling 'mistral task-list' (problematic_task is not there even though system_task_on_error is):
http://paste.openstack.org/show/582938/