Stale relation data over cross-model relation

Hi,

In one of our set ups, we have postgresql deployed and an application deployed in a separate model in K8s. They're related via cross-model relations.

To scale out to beefier units, we did 'juju add-unit' then 'juju remove-unit' to remove the old. Unfortunately, the application on the K8s end, new units, are still trying to talk to the old unit. Even `juju show-unit` is showing stale data. See:

| https://pastebin.canonical.com/p/TwDqnrkRnB/
| https://pastebin.canonical.com/p/spGF9Pssh7/
(apologies, company private)

It seems on leader elected, the charm isn't calling relation-set to update the data passed through the relation. leader-broken/departed for the removed unit should also clear data set via the relation.