The session is timing out when using TFTP to export the running configuration from the firewall.
Resolution:
When sourced from an interface address, TFTP is working as expected as it is a protocol in which the response packets do not have matching ports with the request packets. PAN-OS uses ALG to create a predict session to allow the response packets. However, the response will be treated as Client to Server traffic and must go through a host service check, which will fail. We recommend using SCP to export the configuration.