Angular JS $ http call code returns status code 0

Question

Currently, I came across a strange problem in angular JS when you make an http call. After executing the POST request, after waiting about 2-3 minutes, the call fails, returning:

• status code 0
• null response data

• empty response text

      $.support.cors = true;
      var req = {
          method: 'POST',
          url: serverIp + "UpdateDocumentInventar",
          headers: {
              'codDocument': CodDocument,
              'deviceId': deviceId,
              'authToken': authToken,
              'codGestiune': codGestiune
          },
          timeout: timeoutNR,
          data: articoleChanged   <--- array of items
      }
      var request = $http(req);
  
      return (request.then(handleSuccess, handleError));
  

The web server has not been reached since I put the loggers there to see if there is a problem or not.

I also need to mention that this call does not always fail - sometimes it works, sometimes it is not. (I read on the network that status code 0 is usually associated with not installing CORS - I also installed this, and this is certainly not a problem, as other similar requests are executed correctly).

:  - - http- (60000000)  - HTTP- ( , , 41)

,