Umbraco 7.5.3

I'm attempting to save media via the content service to blob storage and getting a very odd result.

The media service method runs accordingly and performs a save, however the resultant blob has a content length of zero! The odd thing is that the thumbnail blob is present and correct.

The crux of my code is simple enough, I'm matching a string value from within an old umbraco.config file from a site i'm importing from, creating a web request for that image and saving the resultant response to the media service. Nothing crazy as far as I can see.

Match inlineImageMatch = urlRegex.Match(inlineImage);
if (inlineImageMatch.Success)
{
    inlineImage = string.Join(string.Empty, rootUrl.TrimEnd("/"), inlineImageMatch.Value);

    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(inlineImage);
    WebResponse response = null;
    try
    {
        using (response = request.GetResponse())
        {
            IMedia image = mediaService.CreateMedia(Path.GetFileNameWithoutExtension(inlineImage), mediaRootId, Constants.Conventions.MediaTypes.Image);

            using (Stream stream = response.GetResponseStream())
            {
                using (MemoryStream ms = new MemoryStream())
                {
                    stream.CopyTo(ms);
                    ms.Flush();
                    image.SetValue(Constants.Conventions.Media.File, Path.GetFileName(inlineImage), ms);
                    mediaService.Save(image, 0, false);
                    inlineImageId = image.Id;
                }
            }
        }
    }
    catch (Exception ex)
    {
        response?.Dispose();
    }
}

I'm using my own FileSystemProvider within the website to push to Azure. As far as I am aware the same calls would be made using both the media service and the backoffice - Which works, so I'm ruling that out.

Anybody got any ideas? Looks like a bug in Umbraco to me.

Here's a screenshot of a blob upload in the explorer.