A domain pair has been created, some users migrated in a pilot project. Later this domain pair was deleted and created again, same users remigrated, but permissions given to these users don't get processed when resource processing is ran. When using custom map dialog on RUM group properties, these users don't show up. When going to Tools->Export to ini, users do appear in the exported .ini file.
This is a known issue with Resource Updating in Migration Manager 8.7 and earlier. When a domain pair has been deleted, it is not enumerated by resource processing anymore and all objects under it are also excluded. Remigrating users does not help because object pairs already exist in ADAM database and are not marked as deleted.
A workaround is to run synchronization for these users, then they will be re-added to resource processing.
This issue will be fixed in Migration Manager 8.8 or later.