Stopping PEX Business Service with python Director class

I'm using the PEX framework to create non-polling Business Services in Python. Below is the code I've used to instantiate my Python Business Service from the application I have written:

conn = iris.connect(...)
IRIS = iris.createIRIS(conn)
#...#
pexserv = iris.pex.Director.CreateBusinessService(conn, "Demo.PEX.FlaskPEXService")
response = pexserv.ProcessInput(record_id)
IRIS.close() # Release IRIS obj
conn.close()
Python
Python

The Service works fine, messages are received properly by the target Business Process as defined by my PEX service, however, every time I run Director.CreateBusinessService(), the created job terminates 'unexpectedly' once I close the IRIS connection.

This is the result of submitting 10 messages through my Python application:

What is the best way of safely 'releasing' the instance of my proxy business service from the Python app? The Director.py class doesn't have any inbuilt methods for releasing a created business service.

Summary: I can create new services without limit, but I can't kill them cleanly before closing the IRIS connection.