This functionality is intended to be set up and used upon adding a new collection. For syncing to work the collection must be synced regularly in small batches. It was really only intended to be used when a Repository base URL needs to be changed. Repositories with lots of unsynced records may fail to complete unexpectedly.
Libraries needing to update information in their repository records, use the Replace all Record Processing type to update your WorldCat records with updated data. Libraries needing to update their Repository base URL will need to delete all earlier records and reload the repository instead.
There is more on WorldCat Sync setup.