Problems restarting docker from CLI

I'm managing my server from 12,000 miles away and have only a neighbor available to do a pushbutton reboot should things need it.  So I'm a little restricted in what I can do to manage the unexpected.

Recently one of my images (needo's SABnzbd) has been giving me trouble.  The symptom is that the WebUI stops loading.  OK, so I'll restart the container. No problem, except I'm unable to shut down (or restart) the container using either the unraid WebUI or the CLI.  I can kill it by killing processes labeled "docker" on the server, though sometimes this crashes the server.  However, even if I kill it, I can't restart Docker and can't restart the server because /mnt/cache is not unmountable.  Powerdown or reboot usually results in an unresponsive server requiring a powerbutton reboot; the webUI hangs on "unmounting array".

I can get into the container with docker exec -it.  I can kill sabnzbd with kill -9 <pid> and it shows the process as <defunct>  But I can't seem to unmount the config directory on /mnt/cache (at /dev/sdk1):

"umount: /config: must be superuser to umount"

I'm root in the container, and can't figure out what a superuser is in this context. I suspect I will also have a hard time rebooting or shutting down the system within the container<edit: Yes, I am unable to reboot or shutdown or halt>.

Q:  How can I unmount a mount within a container?  superuser???

I did seem to be able to kill docker entirely (shut down all other containers, then identify the remaining processes (2) that are labeled docker.  I'm pretty sure which one maps to this container based on uptime.  If I kill these, I hope to be able to restart docker, though I'm not sure if the /mnt/cache mount will remain locked up.  There is no unRAID webUI page for docker in this instance.

Q: how do you restart docker from scratch using the CLI?

Finally, I'm not sure what's going on with this container.  It's been stable for a year or so, and I have tried rebuilding it, even deleting the image and downloading fresh image from the repository. Mappings have not changed, or anything else in the container.

Your advice will be appreciated;

Dennis

UnRAID 6.0.0