But you are getting an error because the chunk is actually missing on the S3 object store, so this is not a bug but that snapshot being corrupt. Can you maybe see if that chunk was incorrectly flagged as corrupt by checking if a corresponding object with a .0.bad extension exists on your S3 object store to be located in <datastore-name>/.chunks/3cef/. If that is the case, try renaming that object by dropping the extension and do a re-verify of that snapshot.
