If the "create" command is used to create a collection, the field "create" is included as the first collection option in the collection's system.namespaces entry. If the collection options are later modified, the internal update to the system.namespaces collection can re-order the "create" field such that it no longer appears first. Dumping/restoring this collection will subsequently not succeed: mongorestore will send a garbled command to the server upon attempting to re-create the collection, as it assumes that "create" is the first element in the options document (if it appears at all).
Dumping/restoring this collection fails with "no such command: capped".
This does not affect mongod 2.5.x, since the update refactor causes updates to no longer re-order fields.
Original ticket description: