List<IMultipartFormSection>を設定したUnityWebRequest.uploadHandlerのメモリリーク

public IEnumerator mediaUpload()
{
    // /media
    string l_url = _urlMain + "/media";

    // リソースをアンロードする.
    System.GC.Collect();
    Resources.UnloadUnusedAssets();
    yield return null;

    string _path = l_save1_path = UnityEngine.Application.persistentDataPath + "/" + UnityEngine.Application.productName + "/" + "updata.mp4";

    // ファイル読み込み
    byte[] l_file_data = File.ReadAllBytes( _path );
    string l_fileName = "hoge.mp4";

    var request = new UnityWebRequest( l_url, "POST");
    setRequest( request );
    // タイムアウト設定
    request.timeout = 300;

    List<IMultipartFormSection> requestData = new List<IMultipartFormSection>();
    requestData.Add( new MultipartFormFileSection( "file", l_file_data, l_fileName, "video/*" ) );

    if( 0 < user_id )
        requestData.Add( new MultipartFormDataSection( "user_id",               user_id.ToString() ) );
    if( 0 < player_id )
        requestData.Add( new MultipartFormDataSection( "player_id",             player_id.ToString() ) );
    if( 0 < group_id )
        requestData.Add( new MultipartFormDataSection( "group_id",              group_id.ToString() ) );
    if( 0 < team_id )
        requestData.Add( new MultipartFormDataSection( "team_id",               team_id.ToString() ) );
    if( 0 < game_id )
        requestData.Add( new MultipartFormDataSection( "game_id",               game_id.ToString() ) );

    if( !title.Equals( "" ) )
        requestData.Add( new MultipartFormDataSection( "title",                 System.Text.Encoding.UTF8.GetBytes( title ) ) );
    if( !comment.Equals( "" ) )
        requestData.Add( new MultipartFormDataSection( "comment",               System.Text.Encoding.UTF8.GetBytes( comment ) ) );

    byte[] boundary = UnityWebRequest.GenerateBoundary();
    byte[] formSections = UnityWebRequest.SerializeFormSections( requestData, boundary );

    // データ設定
    request.uploadHandler   = (UploadHandler) new UploadHandlerRaw( formSections );
    request.downloadHandler = (DownloadHandler) new DownloadHandlerBuffer();

    // ヘッダを設定
    request.SetRequestHeader("X-Requested-With", "XMLHttpRequest" );
    request.SetRequestHeader("Content-Type", "multipart/form-data; boundary="+System.Text.Encoding.UTF8.GetString(boundary) );
    request.SetRequestHeader( "Authorization", "Bearer "+ _access_token );
    // アプリ名、Ver、プラットフォーム
    request.SetRequestHeader("X-Escore-Env", "app="+APP_NAME+"; ver="+VER+"; os="+isOS() );

    yield return request.Send();

    // 通信エラーチェック
    if(request.isNetworkError){
        Debug.Log("mediaUpload()::Error = " + request.error );
        // UTF8文字列として取得する
        string l_file = request.downloadHandler.text;
        Debug.Log("mediaUpload()::l_file = "+l_file );
    }else{
        Debug.Log("mediaUpload()::complete!---------------------->>>>");

        // UTF8文字列として取得する
        string l_file = request.downloadHandler.text;
        Debug.Log("mediaUpload()::l_file = "+l_file );
    }
}