Error

giving me this error after some ajax requests, it seems to be when i make two requests at once, running on windows php 7.1 , any ideias?

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<b>Fatal error</b>:  Uncaught Error: Access to undeclared static property: Phalcon\Di::$_default in C:\xampp\htdocs\kestt.new\config\services.php:16
Stack trace:
0 [internal function]: Phalcon\Di-&gt;__construct()
1 C:\xampp\htdocs\kestt.new\config\services.php(16): Phalcon\Di\FactoryDefault-&gt;__construct()
2 C:\xampp\htdocs\kestt.new\public\index.php(17): require('C:\\xampp\\htdocs...')
3 {main}

Next Error: Access to undeclared static property: Phalcon\Di::$_default in C:\xampp\htdocs\kestt.new\config\services.php:16
Stack trace:
0 [internal function]: Phalcon\Di-&gt;__construct()
1 C:\xampp\htdocs\kestt.new\config\services.php(16): Phalcon\Di\FactoryDefault-&gt;__construct()
2 C:\xampp\htdocs\kestt.new\public\index.php(17): require('C:\\xampp\\htdocs...')
3 {main}
  thrown in <b>C:\xampp\htdocs\kestt.new\config\services.php</b> on line <b>16</b><br />