Иногда мое arduino подключается к базе данных SQL, а иногда нет — почему?

<?php
//require("config.php");
$dbHost = "localhost";
$dbUsername = "root";
$dbPassword = '';
$dbName = "map1";

// Opens a connection to a MySQL server
$connection = mysqli_connect($dbHost, $dbUsername, $dbPassword, $dbName);
if (!$connection) {
die('Not connected : Ah shit ' . mysqli_error());
}

//Set the active MySQL database
$db_selected = mysqli_select_db($connection, $dbName );
if (!$db_selected) {
die ('Can\'t use db : ' . mysqli_error());
}


//$request = $_GET['request'];

//$sql = "INSTERT INTO request.request (request)
//VALUES ('$request', '$request', '$request', '$request', '$request')";


$latitude = $_GET['latitude'];
$longitude = $_GET['longitude'];


//TEST to see if values received.
//$file = "testfile.txt";
//file_put_contents($file,$latitude . "\n");
//file_put_contents($file,$latitude);

$myfile = fopen('testfile.txt', 'a');
fwrite($myfile, "\r\n" . 'Latitude = ' . $latitude . "\r\n");
fwrite($myfile, 'Longitude = ' . $longitude . "\r\n" );
fclose($myfile);

//Delete old GPS location
//$sql = "DELETE FROM markers WHERE type='GPS'";
//Checks to see if row deleted
//if (mysqli_query($connection, $sql)) {
//    echo "GPS record cleared";
//} else {
//    echo "Error: Cant clear record! " . $sql . "<br>" . mysqli_error($connection);
//}

//INSERT into SQL database
$sql = "INSERT INTO markers (name, address, lat, lng, type)
VALUES ('GPS', 'GPS','".$_GET["latitude"]."','".$_GET["longitude"]."', 'GPS')";

// VALUES ('GPSname', 'GPSaddress','$latitude','$longitude', 'GPStype')";
//Checks to see if new record made
if (mysqli_query($connection, $sql)) {
echo "\nGPS record created";
} else {
echo "Error: " . $sql . "<br>" . mysqli_error($connection);
}

mysqli_close($connection);
?>