Chrome headless not completing, ever (Windows) - google-chrome

Question

I'm struggling to get Chrome headless to do absolutely anything.
I've tried the simple 'getting started' here: https://developers.google.com/web/updates/2017/04/headless-chrome
This example: chrome --headless --disable-gpu --screenshot https://www.chromestatus.com/
does nothing for me. No screenshot generated in the folder. (Was running CMD as Admin).
I've created a webapp (running in IIS on my PC) and set a breakpoint on its Index page. When I call the app using Chrome headless the breakpoint is triggered, but my 2nd (Console) app which created the Chrome headless instance never proceeds beyond the 'Navigate()' line.
The code from the console app:
IWebDriver webClient;
ChromeOptions option = new ChromeOptions();
option.AddArguments("--headless", "--disable-gpu", "--window-size=1920,1200", "--ignore-certificate-errors", "--no-sandbox");
webClient = new ChromeDriver(option);
webClient.Navigate().GoToUrl("http://localhost:49709/");
((ITakesScreenshot)webClient).GetScreenshot().SaveAsFile("ChromeScreenshot.png", ScreenshotImageFormat.Png);
Running:
Windows 7 64-bit
Chrome 64-bit 66.0.3359.139
ChromeDriver 2.38
What am I missing?

Answer 1

I've figured out what is causing the issue, but not why or a proper fix for it. Writing this here in case it helps someone in future.
I found by chance that a timeout error would eventually be thrown after 60 seconds:
The HTTP request to the remote WebDriver server for URL http://localhost:51660/session timed out after 60 seconds.
This error was being thrown on the creation of the ChromeDriver object. Note this is an error thrown by Selenium trying to communicate with the Chrome WebDriver, NOT the Navigate() command failing.
I discovered by complete chance that by removing the "--headless" parameter from the options makes everything works fine. I also found that another parameter "--remote-debugging-port=9222" causes it to fail completely, too.
I'm currently assuming these issues are specific to my environment rather than a bug in the ChromeDriver. But, still looking.