UnityWebRequest huge cpu cost

Hi

I've seen similar issues to this pop up a few times, but nothing with any clear solution. I'm making quite a few UnityWebRequests at a certain point in my game - downloading a varied set of objects/textures from a server. After executing the requests, the CPU usage of the editor goes way up high, and never comes down again.

There has been some discussion of a bug to do with quitting when requests aren't finished, but I'm in 5.2.2 here, and I'm seeing the huge cost anyway.

Has anybody else got this? Am I supposed to destroy the web requests potentially? This is an example of my code to GET a request:

     public UnityWebRequest GetWebRequest(string url, WebRequestCallback callback, object user_data = null)
     {
         UnityWebRequest web_request = new UnityWebRequest(url, "GET");
         web_request.downloadHandler = new DownloadHandlerBuffer();
         if (callback != null)
         {
             PendingWebRequest pw = new PendingWebRequest();
             pw.m_request = web_request;
             pw.m_user_data = user_data;
             pw.m_callback = callback;
             m_web_request_queue.Enqueue(pw);
         }
         web_request.Send();
         return web_request;
     }

Basically the request is submitted then placed into a queue of active requests, which is monitored elsewhere. When the request at the front of the queue is completed, the callback is triggered:

             //hand any completed requests to the central server
             int csreqcount = m_web_request_queue.Count;
             for (int i = 0; i < csreqcount; i++)
             {
                 //dequeue pending request and check if done
                 PendingWebRequest pr = m_web_request_queue.Dequeue();
                 if (pr.m_request.isDone)
                 {
                     //done so handle it
                     pr.m_callback(pr.m_request, pr.m_user_data);
                 }
                 else
                 {
                     //not done so requeue it
                     m_web_request_queue.Enqueue(pr);
                 }
             }
 

I see nothing unusual in my code. But I have narrowed down the CPU cost to the web requests and see no way of reducing them