The CachingLookupService currently only updates its cache when a Lookup is saved or deleted.
It doesn't update:
1. related lookups
i.e doesn't add/remove relationships to any cached related lookup
e.g If a lookup 'A' is saved after a relationship to 'B' is added, and 'B' is not saved,
the cached version of 'B' doesn't contain the new relationship.
This is currently not an issue as the UI currently saves both the source and targets of lookup relationships
If a user was to add/delete a LookupRelationship, this is not reflected in the corresponding cached Lookups.
This is currently not an issue as LookupRelationships aren't added/deleted directly.