RAK8212/BG96 tcp close socket anomaly

Here it is:

  atcmd("ATE0").then(function() {// echo off
        return atcmd("AT+CEREG=2"); //turn on extended cereg response for cell tower info
    }).then(function() {
        return new Promise(function(resolve, reject) {
            var n = 60;
            var done = false;
            var i = setInterval(function() {
                at.cmd(options.lte?"AT+CEREG?\r":"AT+CRE­G?\r",500,function(d)
                    {
                        var n = d.split(",")[1]; //1 =connected,5=connected,roaming
                        if (n==1 || n==5)
                        {
                            clearInterval(i);
                            resolve();
                        }
                    });
                if (n-- <= 0) {
                    clearInterval(i);
                    reject("Timeout!");
                }
            }, 1000);
        });
    }).then(function(d) {
        return atcmd("AT+CGATT=1",10000); // attach to GPRS service