[Twisted-Python] twisted threading server has to be stopped with KILL

[snacktime]

I have a server that uses threads, and when run standalone or via
twistd as an application I have to send it a KILL signal if it has
already answered at least one request.  Or in some cases if I just
send it an INT it will stop if it's currently handling a lot of
requests at the time I send it the signal.  Seems like there is
something I am not doing here that I should be when  using threads?

Chris