I observed that with good radio conditions the SF changes at the 6th uplink. My device is powered at night so does not talk during the day. When the device restarts the device keeps the LoraWan session previously opened by not doing the join and implementing a hundred the Fcnt number.

And there after several tests by rising the frequency of uplinks I realize that the SF changes only well after the 50th uplink.

Do you have a solution ?

Thanks in advance,