MTCDT-210L + MTAC-LORA-915 + RN2903A

Hi
I run the set for US 915MHz and I have some problems with OTAA joining. On RN2903 I only launched 8 (from available 64) channels the same as in Conduit global_conf_json (from 903.9MHz to 904.6MHz like in TTN frequency plan). RN2903 for downlink communication frequency must be set (documentation) above the 923.3MHz (like in TTN frequency plan). With this channel settings Conduit can’t join in OTAA. Logs shows that gateway is seeing join requests (they are correct) and he is answering. Gateway is responding at the same frequency he receive the packet (logs shows that). From configuration RN2903 expects responds at frequencies above 923.3MHz but receives answers from the gateway at lower frequencies that it can not accept. I think that this is the problem but I can be wrong. I need help how to make proper US 915MHz global_conf_json to join in 915MHz OTAA with RN2903. Maybe only how to move the downlink frequencies to higher when uplink is at lower freqs. I’m definitely not the first who has this problem and I am asking for help how to deal with it.