When I tried to restore a collection using the curate replacewithaip task, it failed with this message:
Caused by: org.dspace.content.crosswalk.CrosswalkInternalException: Cannot restore Group permissions on object (type=ITEM, handle=null, ID=c91c2950-c032-4806-b253-4f21068e4f0c). The Group named 'COLLECTION_ebb2589a-3b5a-4be7-837b-0c6eb2c5d64a_DEFAULT_READ' is missing from DSpace. Please restore this group using the SITE AIP, or recreate it
The failure resulted in a new collection dso without metadata or children. Manually creating the missing group and running the curation task again fixed the problem.
The missing DEFAULT_READ group does exist. But it was created pre-6.0 and the group name was generated using the legacy id. The crosswalk is attempting a name lookup based on the collection uuid.
This situation is a bit of an edge case, but I think it's resolved by modifying the packager RoleDisseminator to look up the group by legacyId whenever lookup by uuid results in an empty list. This will add the missing DEFAULT_READ group to the disseminated AIP, using the hdl name format (COLLECTION_hdl:123456789/6703_DEFAULT_READ).