Corrupt/broken OwnCloud container

Hey everyone,
I am new to the forum, so bare with me.

Problem: after recent univention-upgrade, OwnCloud stopped working on my private/test server.

Front-end: Service Unavailable
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

Back-end:
Name: ownCloud
Latest version: 10.3.2
Docker container: running.

Troubleshooting (so far):
univention-app register OK
univention-app remove FAILS w/can’t backup data
univention-app install FAILS w/“it’s already installed”
univention-app upgrade FAILS w/same error as before

Notes: there’s something bizarre/consistent about each process. It tries to backup the previous container data, but fails.

Image upgrade script (pre) failed
Storing data for 4.3/owncloud=10.2.1-1 failed
Could not backup container!
Aborting...
Some networks were defined but are not used by any service: appcenter_net
Starting redis    ... 
Starting owncloud ...

Since this is a test environment, I would be okay to simply purge the container, unregister the app and reinstall, but if there’s more appropriate fix, I’ll take that instead.

I am sure I’ll be running into this in my production environments and it would be nice to know the proper way to handle it.

Bumping for good measures…

Anyone, any ideas?