Comment 1 for bug 1899158

$ juju --version
2.7.8-bionic-amd64

The broken unit remove not resolved the issue, adding a new unit resulted in a blocked charm status due to missing mongodb-relation:

$ juju status graylog/4 | grep ^graylog
graylog 3.0.1 blocked 1 graylog jujucharms 44 ubuntu
graylog/4 blocked executing 30 10.70.227.2 9000/tcp Missing relation to: mongodb

However the relation is present based on juju status:

$ juju status --relations | grep graylog: | grep mongodb
graylog-mongodb:database graylog:mongodb mongodb regular