bentoms suggestion worked - leave Server Admin open with the SUS service
running while editing /etc/swupd/swupd.conf file (where the Apple KB
article said to turn off both the service and close the application).
Changes even stuck after a the service...
I'm running into the same issue - every time I relaunch Server Admin
(whether running on the server or remotely) it seems to copy the changed
file into swupd.conf.previous and recreate the old configuration as
swupd.conf. Ironic, huh? What's the CLI ...