The packet forwarder process may exit if the fields in a received packet are not within the expected range. This can happen occasionally and may be caused by the hardware getting in a bad state. This exit on error is the reason for the angel process that restarts the packet forwarder as a child process.
See packet processing starting on line 842
https://github.com/Lora-net/packet_forwarder/blob/v1.4.1/basic_pkt_fwd/src/basic_pkt_fwd.c