Custom ResourceHandler, response stuck in "pending" state

[RadarNyan]

I'm trying to replace my old custom IResourceHandler with a custom ResourceHandler, following https://github.com/cefsharp/CefSharp/wiki/General-Usage#resourcehandler

	public class CustomResourceHandler : ResourceHandler
	{
		private readonly string _filePath;
		private readonly string _mimeType;
		private readonly bool isRangeRequest;
		private readonly int rangeFrom;
		private readonly int rangeTo;

		public CustomResourceHandler(string filePath, string mimeType, string rangeHeader)
		{
			_filePath = filePath;
			_mimeType = mimeType;
			if (rangeHeader != null) {
				isRangeRequest = true;
				if (rangeHeader.Contains(',')) {
					throw new NotImplementedException();
				}
				var range = rangeHeader.Substring(6).Split('-');
				rangeFrom = range[0] == "" ? -1 : int.Parse(range[0]);
				rangeTo   = range[1] == "" ? -1 : int.Parse(range[1]);
			}
		}

		public override CefReturnValue ProcessRequestAsync(IRequest request, ICallback callback)
		{
			Task.Run(() =>
			{
				using (callback) {
					if (isRangeRequest) {
						StatusCode = 206;
						using (FileStream fileStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read)) {
							if (rangeFrom == -1) {
								throw new NotImplementedException();
							}
							fileStream.Position = rangeFrom;
							if (rangeTo == -1) {
								Headers.Set("Content-Range", $"bytes {rangeFrom}-{fileStream.Length - 1}/{fileStream.Length}");
								ResponseLength = fileStream.Length;
								Stream = new MemoryStream((int)ResponseLength);
								fileStream.CopyTo(Stream);
							} else {
								Headers.Set("Content-Range", $"bytes {rangeFrom}-{rangeTo}/{fileStream.Length}");
								int rangeLength = rangeTo + 1 - rangeFrom;
								ResponseLength = rangeLength;
								byte[] responseBytes = new byte[rangeLength];
								fileStream.Read(responseBytes, 0, rangeLength);
								Stream = new MemoryStream(responseBytes);
							}
							Stream.Position = 0;
						}
					} else {
						StatusCode = 200;
						Stream = File.OpenRead(_filePath);
					}
					MimeType = _mimeType;
					//Headers.Set("Cache-Control", "no-store"); // <- Breaks Response
					callback.Continue();
				}
			});
			return CefReturnValue.ContinueAsync;
		}
	}

I'm using it in a ResourceRequestHandler like this:

		protected override IResourceHandler GetResourceHandler(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IRequest request)
		{
			localCacheExists = File.Exists(localFile);
			if (!File.Exists(localFile)) {
				return null;
			}
			var mimeType = Cef.GetMimeType(localFileExtension);
			return new CustomResourceHandler(localFile, mimeType, request.Headers["Range"]);
		}

The headers are received correctly, but the request stucks in the "pending" state in chromium devtools. My old IResourceHandler implementation (with Open / GetResponseHeaders / Read / Cancel / Dispose) works though. What am I missing?

[RadarNyan]

Appraently setting header Cache-Control: no-store breaks things. In my old implementation I didn't add this header... so much time wasted on debugging this.