HttpContent.CopyToAsync hangs occaisionally

Question

We have a Azure WebJob that fires a Timer every 15 seconds to poll an external Xml data feed. The request returns a 2.4 MB XML file with traffic data. Before reading data the method checks the LastModified header value against the value in the last received data - this is in line with recommendations set by the data feed vendor.

The WebJob works for days/weeks without issue but occasionally it will hang whilst reading the XML data into a memory stream for processing. The last entry on the WebJob log is "Starting copy content to memory stream".

    HttpRequestMessage webRequest = new HttpRequestMessage(HttpMethod.Get, feedPath);

using (var _webApiHttpClient = new HttpClient())
{
    _webApiHttpClient.BaseAddress = new Uri(SettingsManager.Instance.BaseUrl);

    _webApiHttpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("*/*"));

    log.WriteLine(webRequest.RequestUri.ToString());
    using (HttpResponseMessage response = await _webApiHttpClient.SendAsync(webRequest, HttpCompletionOption.ResponseHeadersRead))
    {
        var dateReceived = DateTime.Now.ToUniversalTime();
        log.WriteLine("Request result: {0}", response.StatusCode);

        if (response.IsSuccessStatusCode)
        {
            log.WriteLine("Received feed data");
            DateTimeOffset lastRead = new DateTimeOffset();
            if (lastChangedBlob.Exists())
            {
                using (var stream = lastChangedBlob.OpenRead())
                {
                    BinaryFormatter f = new BinaryFormatter();
                    lastRead = (DateTimeOffset)f.Deserialize(stream);
                }
            }

            log.WriteLine("Content last modified {0} and last read {1}", response.Content.Headers.LastModified, lastRead);
            var modified = response.Content.Headers.LastModified;

            if (modified.HasValue && modified.Value > lastRead)
            {

                log.WriteLine("Starting copy content to memory stream");

                using (Stream stream = new MemoryStream())
                {
                    await response.Content.CopyToAsync(stream);
                    log.WriteLine("Copy completed: response.Content.CopyToAsync");
                    // Go back to start of stream to save file to BLOB
                    stream.Seek((long)0, SeekOrigin.Begin);
                    log.WriteLine("Seeked begining of stream ready to ProcessFeed");
                    await ProcessFeed(type, output, queue, log, dateReceived, stream);
                    log.WriteLine("ProcessFeed completed");
                }

....