Missing one of (Loki|filebeat), one of (Prometheus|target|nrpe) relation(s)

### Bug Description

Hello -

When relating COS proxy with various relations the charm will get stuck in "Missing one of (Loki|filebeat), one of (Prometheus|target|nrpe) relation(s)", despite the relations existing.

### To Reproduce

1. Deploy Openstack/PCB
2. Relate cos proxy wiith the following relations
```
- - ceph-dashboard:grafana-dashboard
- cos-proxy:dashboards
- - ceph-mon:prometheus
- cos-proxy:prometheus-target
- - cos-proxy:dashboards
- etcd:grafana
- - cos-proxy:dashboards
- prometheus-grok-exporter:dashboards
- - cos-proxy:dashboards
- prometheus-openstack-exporter:dashboards
- - cos-proxy:dashboards
- telegraf:dashboards
- - cos-proxy:filebeat
- filebeat:logstash
- - cos-proxy:juju-info
- filebeat:beats-host
- - cos-proxy:juju-info
- landscape-client:container
- - cos-proxy:juju-info
- nrpe:general-info
- - cos-proxy:juju-info
- prometheus-grok-exporter:juju-info
- - cos-proxy:juju-info
- telegraf:juju-info
- - cos-proxy:juju-info
- ubuntu-advantage:juju-info
- - cos-proxy:monitors
- nrpe:monitors
- - cos-proxy:prometheus-rules
- telegraf:prometheus-rules
- - cos-proxy:prometheus-target
- telegraf:prometheus-client
- loki:logging
- - cos-proxy:downstream-prometheus-scrape
- prometheus:metrics-endpoint
- - cos-proxy:downstream-grafana-dashboard
- grafana:grafana-dashboard
- - cos-proxy:downstream-prometheus-scrape
- scrape-interval-config:configurable-scrape-jobs
- - cos-proxy-monitors:downstream-prometheus-scrape
- scrape-interval-config:configurable-scrape-jobs
- - cos-proxy-monitors:monitors
- nrpe:monitors
- - prometheus-libvirt-exporter:dashboards
- cos-proxy:dashboards
- - prometheus-libvirt-exporter:scrape
- cos-proxy:prometheus-target
- - prometheus-openstack-exporter:prometheus-openstack-exporter-service
- cos-proxy:prometheus-target
```

3. Observe cos-proxy in blocked state

[Workaround]

To follow

Thank you,
Peter

### Environment

Openstack PCB
Microk8s on OAM network with Metal-LB

### Relevant log output

```shell
to follow
```

### Additional context

_No response_

Start by reproducing the cos-proxy blocked state with the relation set in the issue, then inspect the relation-status handling and relevant charm entry points. Done means cos-proxy recognizes the existing Loki/filebeat and Prometheus/target/nrpe relations and no longer remains blocked; the issue provides no file or test names.

Written by the indexing model from the issue text.