Outline-server down - how to fix? [solved - still...]

Outline-server is down. How can I fix it? (it works now, but I like to ask what would be the most efficient way, what I did worked, but seems clumsy)

I wanted to simply re-install, for that I need to remove the containers, so i did:

docker rm -fv watchtower shadowbox

But got an error message:

Error response from daemon: unable to remove filesystem for 804***bfad5/mounts/shm: device or resource busy

Then I used the brute force method:

docker system prune -a

That worked, And a wget......

There I got stuck with:

> Starting Shadowbox .......................... FAILED
Unable to find image 'quay.io/outline/shadowbox:stable' locally
stable: Pulling from outline/shadowbox

Then I get to:

root@oline01:~# sudo wget -qO- https://raw.githubusercontent.com/Jigsaw-Code/outline-server/master/src/server_manager/install_scripts/install_server.sh | bash
> Verifying that Docker is installed .......... OK
***
> Generating SHA-256 certificate fingerprint .. OK
> Starting Shadowbox .......................... FAILED
Unable to find image 'quay.io/outline/shadowbox:stable' locally
stable: Pulling from outline/shadowbox
605ce1bd3f31: Pulling fs layer
****
1436fe24816f: Pull complete
Digest: sha256:007b8a2***c32891
Status: Downloaded newer image for quay.io/outline/shadowbox:stable
docker: Error response from daemon: Conflict. The container name "/shadowbox" is already in use by container "8049b73810***c3dbfad5". You have to remove (or rename) that container to be able to reuse that name.

I did ftp to /var/lib/docker/containers/

There where 3 directories /var/lib/docker/containers/7a2cf7f*** (+1 more) that didn’t allow, delete, but rename. After the re-name I did:

docker rm -fv watchtower shadowbox   
docker system prune -a   

And installation was fine. Strangely for me, all keys in the manager still work.

I wonder what was going on?