Model migration hangs on "starting"



In an attempt to clean up my controller from this: Model destroy failure; manual clean-up

and to learn more, I have decided to bring up a new controller and migrate what I need from the old one.

Basically, create new controller - migrate a working CDK model - remove the old controller which has broken stuff in the db.

Yesterday, I followed the instructions at Migrating models

Since I ran the migrate command, nothing seems to happen.

    current: busy
    message: 'migrating: starting'
    since: 16 hours ago
    migration: starting
    migration-start: 16 hours ago

Where can I find out more?
The debug-log of the controller contains a repeated, single message that I also had before the migration, and afaik did not prevent juju from working:

WARNING juju.worker.peergrouper multiple usable addresses found
run "juju config juju-ha-space=<name>" to set a space for Mongo peer communication preserving member with unchanged address [...]

Am I missing something? Is there a way to cancel the migration?