series_seq_not_monotonic· reason_code· applies to schema_validation, state_resolutionA PUT /_arkret/self/keys/backups/{backup_id} request whose `series_seq` is not strictly greater than the current maximum sequence within the same (actor_id, series_id), or whose genesis envelope sets series_seq != 0. See zh/crypto-media/device-lifecycle.md §12.1.