Node-RED & LoRa: duplicate messages

Good Day.

We see instances where the Conduit receives the LoRa packet from the xDot end-node device, but the xDot is not receiving the ACK sent by the Conduit. So the xDot resends the same packet.

Can Node-RED use message metadata like message.fcnt or message.ack to detect duplicate messages and not pass the same message on, for example, using MQTT?

Also, are those message metadata fields defined in detail anywhere?

Thanks in advance for any help!

Best Regards,
William Laing