Neutron-api stuck in config-changed hook failed with sqlalchemy error during functional testing

When running charm-designate dev-basic-bionic-rocky functional tests, my neutron-api instance got sometimes stuck on config-changed hook failed. The error seems to be intermittent as I reproduced twice in 3 runs.

Ran same scenario on bionic-queens one time and it worked with no errors.

Environment:
charm-designate -> running functional tests checked from git.openstack.org directly
Juju version -> 2.5-beta1-bionic-amd64

Here is the error log --> https://pastebin.ubuntu.com/p/ns6S9v6j2X/

The error at the end is: sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) Cannot add a NOT NULL column with default value NULL [SQL: u'ALTER TABLE address_scopes ADD COLUMN ip_version INTEGER NOT NULL']

It looks like my neutron-api is using sqlite instead of percona-cluster, as assigned for this test scenario. In fact, my functional test log gets stuck on application deployment phase and fails as neutron-api failed, and did not execute the relationship phase (which happens just after)

Tried to set manually the relationship between percona-cluster and neutron-api and got:
https://pastebin.ubuntu.com/p/G5QKTThKnr/

/etc/neutron/neutron.conf after relationship set:
https://pastebin.ubuntu.com/p/2R65ZsgwbQ/
Still got connection database set to sqlite, although relationship with percona-cluster was set.

/etc/neutron/plugins/ml2/ml2_conf.ini:
https://pastebin.ubuntu.com/p/NF9KfgGqgF/

Re-running neutron-db-manage command by hand leads to:
https://pastebin.ubuntu.com/p/MdbNyNZ8jP/

On Bionic-Queens scenario, neutron.conf was correctly set to connect with mysql database.
The bug is similar to: https://bugs.launchpad.net/neutron/+bug/1697881 but DB-neutron api relation was supposed to set connection info correctly and move away from sqlite.