I've had this issue on and off with the sabnzbdvpn image for a while now, and just recently I've been unable to workaround it anymore.
The issue is twofold.
First, starting the image does not start sabnzbd for me. As in, there is not even an attempt to start it in the logs:
And it will just sit there, forever, cycling on the inactivity timeout. I can manually start the sabnzbd process by exec'ing into the container and running '/opt/sabnzbd/SABnzbd.py -f /config/sabnzbd.ini'. This launches sab and I can access the webUI.
However, now I have a second problem - as of today, when trying to relaunch the container and start sab manually again, while sab launches it now reports it has no public IPv4 address. I am able to ping external addresses via IP address, but not using an FQDN.