Gateway looks like doesn't receive packet

We used the docker set up a lorawan server on Ubuntu 16.04. The gateway used RAK831+RPI3. first we was configured the gateway on the TTN server, It looked like everything was ok and the data frame was received, but when I changed to the IP of the lorawan server, We can’t get any data frames. We’ve done some checking according to the debug instructions, but there is no clear clue.

If I do not start docker-compose, tcpdump on ubuntu can receive UDP packet at port 1700, but after all docker starts, tcpdump on loraserver gateway bridge only catch several packets on 1700 port when packet-forwarder start time.

What method should I continue to check next?