Multi node communication

Hi All,
I am using the below version for Lora communications

  1. chip stack network server:3.10
  2. chip stack application server:3.13
  3. Lora-gateway-bridge:3.8
    I have Two nodes(sx1272) which are having AT Command Firmware and I configured them for OTAA mode.
    two nodes are sending data with a 3-sec delay, after some time one node stops sending data. The retransmission mechanism is there on the node side but 8 times retransmission is happening while doing retransmission concentrator is taking data from the other node.
    please help me to solve this.