Thanks once more.
My gateway runs the forwarder software from (“/bokse001/dual_chan_pkt_fwd”) but issues at this level was : packets received at the gateway layer on a frequency such as 866.1 or any other frequency different from 868.3 were all shown in the gateway logs as packets sent on the frequency 868.3, as a result, the server routes the downlink packets to that frequency. That should be where my problem lies.
I have carried out some modification on the gateway ( setting the _STRICT_1CH = 1 instead of _STRICT_1CH =0 which was the default value).
I am still about to test it on my node.
Thanks for your support.