When a query yields it releases its snapshot, and any point-in-time instantiated collections stored on the snapshot decoration are destructed. At the start of a query, collections are fetched using a namespace. However, when a query is restoring from yield it attempts to fetch collections by UUID. It's possible for a UUID to no longer resolve to a namespace in the latest collection catalog if that collection was dropped while the query was yielding. This doesn't conclude that the collection is inaccessible at an earlier point-in-time as the data files may still be on disk.