Ran into this as well, Juju 2.7.6.
| ubuntu-repository-cache/1 waiting allocating 3 10.25.22.6 agent initializing
| $ JUJU_DEV_FEATURE_FLAGS=developer-mode juju dump-model | ERROR missing relation scope for ubuntu-repository-cache:cluster and ubuntu-repository-cache/1
Ran into this as well, Juju 2.7.6.
| ubuntu- repository- cache/1 waiting allocating 3 10.25.22.6 agent initializing
| $ JUJU_DEV_ FEATURE_ FLAGS=developer -mode juju dump-model repository- cache:cluster and ubuntu- repository- cache/1
| ERROR missing relation scope for ubuntu-