OTAA join failed for SF10

Hi guys,
I’m testing the effect of spreading factor on the range coverage. I’m using the repo from https://github.com/matthijskooijman/arduino-lmic with OTAA connection and single frequency of 923.3MHz. What I have done was changing the data rate in lmic.c -> initJoinLoop -> setDrJoin(DRCHG_SET, DR_SF10);
It works perfectly fine for SF7,SF8 and SF9 but for SF10, the join request is not successful.

For SF9, the request join instantly.

I have tried many other ways suggested in the forum like
but it does not work for me. Anyone has any idea on how to solve this?
I’m using LoRa gateway LG01 and 915MHz LoRa shield with SX1276 chips by Semtech

I’m sorry, that is a single-channel forwarder and not a proper LoRaWAN gateway. You should not use that on TTN (so please disconnect it), and questions about that are off topic here.