Webapi action invoked twice from single request

Question

I have a method in a .NET api-controller that is invoked twice from a single request (the request is made from the http module in angular). Everything works fine (the action is invoked once) locally on my machine running the application on iis express. The issue occurs when the application is run in our test-environment. This environment consist of an IIS 8 server running behind a netscaler reverse proxy. Using fiddler I get a note on the statistics tab saying "NOTE: This request was retried after a Receive operation failed.".

This is the action that is invoked twice:

    [HttpPut]
    [Route("orders/anull/{id}")]
    public IHttpActionResult Anull(string id)
    {
        if (!_orderRepository.Anull(id))
        {
            return Content(HttpStatusCode.Gone, "The order could not be anulled. Ensure that the order hasn't already been anulled by reloading the page or contact developers.");
        }
        return Content(HttpStatusCode.NoContent, "Order was anulled");
    }