在访问 Web 资源的 DispatcherTimer 上运行的 Async-Await 函数会定期失败

我在 DispatcherTimer 上运行了一个异步 lambda 来从 Web API 获取数据。我的代码如下：

_timelineSeekTimer = new DispatcherTimer();
_timelineSeekTimer.Interval = TimeSpan.FromMilliseconds(500);
_timelineSeekTimer.Tick += async (e, o) =>
{
    var sw = new Stopwatch();
    sw.Start();
    Console.WriteLine("Init: " + sw.ElapsedMilliseconds);
    // Get HttpResponseMessage from VADAAR API
    var response = await VadaarExtensions.CenPostAsync("/viewers/" + Viewer.GetName() + "/canvases/default/renderers/01/time", "GETPAYLOAD");
    Console.WriteLine("Response Time: " + sw.ElapsedMilliseconds);
    // Extract JSON string from response
    var responseBodyAsText = await response.Content.ReadAsStringAsync();
    // Extract time value from JSON with regex @TODO: Not use regex
    var parseJsonTime = Regex.Match(responseBodyAsText, @"('d+)}").Groups[1].Value;
    ulong timeUs = ulong.Parse(parseJsonTime);
    TimelineSec = timeUs * 1e-6;
    Console.WriteLine("Current Seek Time: " + TimelineSec);
};

我的问题是计时器运行得越快，函数开始失败。下面是函数的示例输出：

Init: 0
Response Time: 14
Current Seek Time: 0.543245
<snip>
Init: 0
Response Time: 18
Current Seek Time: 8.668584
Init: 0
Init: 0
Response Time: 887
Current Seek Time: 10.553811
<snip>
Init: 0
Response Time: 885
Current Seek Time: 18.67975
Init: 0
Init: 0
Response Time: 1760
Current Seek Time: 20.56805

当对 API 使用基于浏览器的 GUI 时，响应时间在 15-30 毫秒之间。这些故障的解释是什么，为什么每次失败的响应时间都会变差？