C# RemoteWebDriver: Content-Type header is missing exception when using alpha-7 #1145

🐛 Bug Report

Getting Content-Type header is missing exception when trying to use RemoteWebDriver on C#. It seems like relax-checks flag does not work as expected.

The probles reproduces on local docker and on Kubernetes env.

To Reproduce

1. Follow the steps described in Readme:

docker network create grid
$ docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4.0.0-alpha-7-20201119
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -v /dev/shm:/dev/shm \
    selenium/node-chrome:4.0.0-alpha-7-20201119
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -v /dev/shm:/dev/shm selenium/node-firefox:4.0.0-alpha-7-20201119
$ docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub \
    -e SE_EVENT_BUS_PUBLISH_PORT=4442 \
    -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 \
    -v /dev/shm:/dev/shm selenium/node-opera:4.0.0-alpha-7-20201119

2. Try to use the grid

Expected behavior

It should be possible to run tests using RemoteWebDriver

Test script reproducing this issue (when applicable)

var options = new ChromeOptions(); options.AddUserProfilePreference("download.default_directory", DownloadDirectory); options.AddUserProfilePreference("intl.accept_languages", " en-GB"); options.AddUserProfilePreference("disable-popup-blocking", "true"); options.AddUserProfilePreference("profile.default_content_settings.popups", 0); options.AddUserProfilePreference("profile.default_content_settings.multiple-automatic-downloads", 1); options.AddUserProfilePreference("download.directory_upgrade", true); options.AddUserProfilePreference("download.prompt_for_download", false); options.AddUserProfilePreference("download.extensions_to_open", ""); options.SetLoggingPreference("Browser", LogLevel.All);.
options.AddArgument("--headless");
options.AddArgument("--no-sandbox");
options.AddArgument("--disable-dev-shm-usage");
options.AddArgument("--window-size=1920,1080");
driver = new RemoteWebDriver(new Uri("REMOTE_URL_GOES_HERE"), options.ToCapabilities(), TimeSpan.FromSeconds(10000));

Environment

OS: Windows 10
Docker-Selenium image version: 4.0.0-alpha-7-20201119
Docker version: 19.03.13, build 4484c46d9d