The nodes (several only transmitting temp/hum) seems hangs, they don't interest if I did restart or no the gateway//controller.

I would implement some check of uplink available on the sketchs, on the loop. If uplink is available, transmit, if not, recheck.

But... I don't know how to implement this check.

Can you help me with this?

My pseudocode could be:

void loop() {
    bool is_available_uplink;
    is_available_uplink = getUplinkState();
    if (is_available_uplink) {
        // do stuff
    }
}

bool getUplinkState() {

    bool is_uplink_available = false;
   
    // check here the uplink
    return is_uplink_available;

}

Thank you to all!