Application server only send the 1st packet of the 3 to the network server

—here is the application server log with debug turned on:
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=info msg=“integration/mqtt: downlink event received” topic=application/7/device/60c5a8fffe781ee8/command/down
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“sql query executed” args="[[96 197 168 255 254 120 30 232]]" duration=5.01035ms query=“select * from device where dev_eui = $1 for update”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“sql query executed” args="[60c5a8fffe781ee8]" duration=5.191216ms query="\n\t\tselect\n\t\t\tns.*\n\t\tfrom\n\t\t\tnetwork_server ns\n\t\tinner join device_profile dp\n\t\t\ton dp.network_server_id = ns.id\n\t\tinner join device d\n\t\t\ton d.device_profile_id = dp.device_profile_id\n\t\twhere\n\t\t\td.dev_eui = $1"
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=warning msg=“creating insecure network-server client” server=“localhost:8000”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“parsed scheme: “””
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“scheme “” not registered, fallback to default scheme”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“ccResolverWrapper: sending update to cc: {[{localhost:8000 0 }] }”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“base.baseBalancer: got new ClientConn state: {{[{localhost:8000 0 }] } }”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“Subchannel Connectivity change to CONNECTING”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“base.baseBalancer: handle SubConn state change: 0x36aa410, CONNECTING”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“Channel Connectivity change to CONNECTING”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“Subchannel picks a new address “localhost:8000” to connect”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“Subchannel Connectivity change to READY”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“base.baseBalancer: handle SubConn state change: 0x36aa410, READY”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“roundrobinPicker: newPicker called with info: {map[0x36aa410:{{localhost:8000 0 }}]}”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“Channel Connectivity change to READY”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=info msg=“finished client unary call” ctx_id="" grpc.code=OK grpc.ctx_id=ee5ffb82-296c-4fe7-99d8-d27619173120 grpc.duration=16.798059ms grpc.method=GetNextDownlinkFCntForDevEUI grpc.service=ns.NetworkServerService span.kind=client system=grpc
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=debug msg=“sql query executed” args="[[96 197 168 255 254 120 30 232]]" duration=1.869581ms query=“select * from device where dev_eui = $1”
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=info msg=“integration/mqtt: downlink event received” topic=application/7/device/60c5a8fffe781ee8/command/down
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=info msg=“finished client unary call” ctx_id=931d2669-0ee8-4eaf-bea5-b297a0030999 grpc.code=OK grpc.ctx_id=f00162c2-833c-4156-981c-7a78d86d1a58 grpc.duration=17.041516ms grpc.method=CreateDeviceQueueItem grpc.service=ns.NetworkServerService span.kind=client system=grpc
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=info msg=“downlink device-queue item handled” confirmed=false dev_eui=60c5a8fffe781ee8 f_cnt=162
Feb 09 16:05:43 raspberrypi chirpstack-application-server[11825]: time=“2021-02-09T16:05:43-08:00” level=info msg=“integration/mqtt: downlink event received” topic=application/7/device/60c5a8fffe781ee8/command/down
^C
pi@raspberrypi:/usr/local/lora-net $

—if I put 1 second sleep in between the mqtt_publish, all packets will arrive at networking server successfully