Comment 17 for bug 1952414

There *is* a correlation. At the end of the day, it might be boiled down to the known issue to other charms than API services...
https://bugs.launchpad.net/charm-layer-ovn/+bug/1896630

In another run, there are two units that failed to put /etc/apache2/ssl/keystone/cert_<vip> and those two had FQDN compared to the succeeded one with hostname.

$ for i in {0..2}; do echo keystone/$i; juju ssh keystone/$i 'ls -l /etc/apache2/ssl/keystone/cert_192.168.151.99' 2>/dev/null ; done
keystone/0
ls: cannot access '/etc/apache2/ssl/keystone/cert_192.168.151.99': No such file or directory
keystone/1
lrwxrwxrwx 1 root root 50 Mar 23 07:13 /etc/apache2/ssl/keystone/cert_192.168.151.99 -> /etc/apache2/ssl/keystone/cert_juju-3f0619-1-lxd-0
keystone/2
ls: cannot access '/etc/apache2/ssl/keystone/cert_192.168.151.99': No such file or directory

$ juju show-unit vault/0 --endpoint certificates
vault/0:
  workload-version: 1.8.8
  machine: 0/lxd/2
  opened-ports:
  - 8200/tcp
  public-address: 192.168.151.200
  charm: ch:amd64/jammy/vault-93
  leader: true
  life: alive
  relation-info:
  - relation-id: 10
    endpoint: certificates
    related-endpoint: certificates
    application-data: {}
    related-units:
      keystone/0:
        in-scope: true
        data:
          cert_requests: '{"juju-3f0619-0-lxd-0.maas": {"sans": ["192.168.151.122",
            "192.168.151.99"]}}'
          egress-subnets: 192.168.151.122/32
          ingress-address: 192.168.151.122
          private-address: 192.168.151.122
          unit_name: keystone_0
      keystone/1:
        in-scope: true
        data:
          cert_requests: '{"juju-3f0619-1-lxd-0": {"sans": ["192.168.151.125", "192.168.151.99"]}}'
          egress-subnets: 192.168.151.125/32
          ingress-address: 192.168.151.125
          private-address: 192.168.151.125
          unit_name: keystone_1
      keystone/2:
        in-scope: true
        data:
          cert_requests: '{"juju-3f0619-2-lxd-0.maas": {"sans": ["192.168.151.197",
            "192.168.151.99"]}}'
          egress-subnets: 192.168.151.197/32
          ingress-address: 192.168.151.197
          private-address: 192.168.151.197
          unit_name: keystone_2