What channel plan are you using?
I will assume EU868
Are you using 1.4.1 or 1.4.3 or both act the same?
Both look like mac command answers
0703 is a new channel request answer
0307 is an adr command answer
The updated network server sends down a packet in the first downlink to define channels for DR6 and DR7
What port is the packet being received on from the end-device?
If the FOpts is empty and the payload contains MAC commands it should be received on port 0.
Packets sent using port 0 should not be forwarded to the application.
How is your application receiving packets in node-red? MQTT node or LoRa-IN node? Can you post an example of the json received.