>The terminating event is triggered by SAP standard
This was exactly my point. You might spend hours & days of investigating the task/workflow/event/event queue, but the reason behind might be that there is a bug in the standard code, and it is not triggering the event in some rare circumstances. I cannot help much in this, I just wanted to point out that you might be looking for your solution in a wrong place (task, WF-BATCH, event queue).
I've a feeling that I have seen something similar. This was years ago, so I cannot remember any details. I just remember that we might have put some kind of condition check in the CATS workflow, meaning that if the approval work item was not completed even all the time entries were approved/handled, we just completed the workflow (or the task) (never found the reason for the behavior).
Kind regards,
Karri