# Send failed since rewinding of the data stream failed

I'm using WWW class to sent a WWWForm to an asp.net server.
it used to work in unity 5.3.x but since I migrated to 5.6.3f1, it is not working and sending Send failed since rewinding of the data stream failed message.
I tried doing it with the UnityWebRequest but it couldn't send the data in the form and I would get null values in the server side. here is my code:


WWWForm WF = new WWWForm();
//I'm sending some json as strings. I don't need to do anything to the json data on the server
WWW www =new WWW(ServerProperties.ServerAddress + "/Unity/SaveDesign", WF);
while (!www.isDone)
{
yield return www.progress;
}
if (www.error != null)
debug.Log(www.error);
else
debug.Log(www.text);


And I'm getting this request with [HttpPost] on the server.


[HttpPost]
public ActionResult SaveDesign(DesignViewModel _Design)


I'm reaching a deadline and I really need this, any ideas is appreciated.