However, on startup, it is possible that the underlying NATS cluster is not fully formed. The server would not get any response from the rest of the cluster and therefore start successfully and service clients. Anytime a Streaming server detects that a NATS server was added to the NATS cluster, it will resend its list of channels. It means that currently running servers may suddenly fail with a message regarding duplicate channels. Having the same channel on different servers means that a subscription would be created on all servers handling the channel, but only one server will receive and process message acknowledgements. Other servers would then redeliver messages (since they would not get the acknowledgements), which would cause duplicates.