Delayed downlink messages in gateway bridge

Hi Experts!
I am facing an issue with the Lora gateway. The client sends an uplink message which is processed on the network server.
The network server sends a downlink message back to the client. This message arrives at the gateway but is delayed (2-5 seconds) or dropped.
to be more precise i observe the below from the Gateway Bridge Log:

Down frame on the MQTT topic
time=“2021-11-17T12:08:02.400196316+01:00” level=info msg=“integration/mqtt: downlink frame received” downlink_id=8a48da5d-46e2-48c7-a2c9-7c6093c72af2 gateway_id=cc028d20254ef002
time=“2021-11-17T12:08:02.400522107+01:00” level=debug msg=“sending message to gateway” gateway_id=cc028d20254ef002 message="{“msgtype”:“dnmsg”,“DevEui”:“01-01-01-01-01-01-01-01”,“dC”:0,“diid”:35400,“pdu”:“60f955c000a513000352ff0001f0bafc66”,“priority”:1,“RxDelay”:1,“RX1DR”:4,“RX1Freq”:868100000,“RX2DR”:0,“RX2Freq”:869525000,“xtime”:45317472929820996,“rctx”:0}"
time=“2021-11-17T12:08:02.4007861+01:00" level=info msg=“backend/basicstation: downlink-frame message sent to gateway" downlink_id=8a48da5d-46e2-48c7-a2c9-7c6093c72af2 gateway_id=cc028d20254ef002
[ 7 Timesync Messages zwischen Common Packet forwarder und Gateway Bridge ]
time=“2021-11-17T12:08:03.877385059+01:00” level=debug msg=“backend/basicstation: message received” gateway_id=cc028d20254ef002 message=”{“msgtype”:“dntxed”,“seqno”:35400,“diid”:35400,“DR”:0,“Freq”:869525000,“DevEui”:“01-01-01-01-01-01-01-01”,“rctx”:0,“xtime”:45317472931820996,“txtime”:6081.597612,“gpstime”:0}”
time=“2021-11-17T12:08:03.877633972+01:00” level=info msg=“backend/basicstation: downlink transmitted message received” downlink_id=8a48da5d-46e2-48c7-a2c9-7c6093c72af2 gateway_id=cc028d20254ef002
time=“2021-11-17T12:08:03.878014362+01:00” level=info msg=“integration/mqtt: publishing event” downlink_id=8a48da5d-46e2-48c7-a2c9-7c6093c72af2 event=ack qos=1 topic=gateway/cc028d20254ef002/event/ack

There is a time difference of 1.476 seconds between “downlink-frame message sent” to gateway and “downlink transmitted message received”.

  1. please help me to understand the factors which contribute to the above delay.
  2. kindly provide me documentation if any to understand the downlink message flow along with the explanation for every field of the downlink message in gateway bridge. Thanks in advance!