ajax satuts cancelled after some attempts - php

Question

im making and update in mysql table when button click, the problem is ajax jquery not working sometimes. It works fine and somehow after x attempts it stop working and stars cancelling my pettitions
my jquery code:
$.ajax({
type:'GET',
url: 'php/updateCosto.php',
data:{
obrero: $obrero,
fechai: $fechaa,
fechaf: $fechab,
costo: $costoS,
},
success: function(result){
if (result == 1) {
alert('Registro Actualizado');
location.reload(true);
}else {
console.log("no actualizado entrada");
alert('Registro No Actualizado');
location.reload(true);
}
}
}); // fin del ajax
the php one:
<?php
include('../db/conn.php');
$maestro = mysql_real_escape_string($_GET['obrero']);
$costosemanal = mysql_real_escape_string($_GET['costo']);
$fechai = mysql_real_escape_string($_GET['fechai']);
$fechaf = mysql_real_escape_string($_GET['fechaf']);
$update = "UPDATE tbl_costos
SET costo_semanal = '$costosemanal'
WHERE fechai = '$fechai'
AND fechaf ='$fechaf'
AND obrero = '$maestro'";
$result = mysql_query($update);
$rows = mysql_affected_rows();
echo ($rows);
mysql_free_result($result);
?>
the problem is after x number of attempts the success part of ajax object is not being used and im getting the STATUS (canceled) from network.
I dont know if it is an issue of CORS AJAX pettition or something!!