Another thought...
Perhaps 'async_task_route()' automatically creates a transaction, which is why I
was having problems with the calls to 't_newtran()' and 't_release()'
after the route had been changed to execute through 'async_task_route()'.
If so, then maybe it's safe for my async presence route to not call
't_newtran()' and 't_release()'.
Thanks.