As described in https://github.com/electron/electron/pull/13769, we had to disable mixed sandbox related tests for Windows CI. We should re-enable them back after finding out the root reason.
atom/app/atom_main_delegate.cc
const bool initialized = ui::ResourceBundle::HasSharedInstance();
  if (initialized)
    ui::ResourceBundle::CleanupSharedInstance();
  
  base::FilePath pak_dir;
#if defined(OS_MACOSX)
  pak_dir =
      base::mac::FrameworkBundlePath().Append(FILE_PATH_LITERAL("Resources"));
#else
  base::PathService::Get(base::DIR_MODULE, &pak_dir);
#endif
  ui::ResourceBundle::InitSharedInstanceWithLocale(
      locale, nullptr, ui::ResourceBundle::LOAD_COMMON_RESOURCES);
  ui::ResourceBundle& bundle = ui::ResourceBundle::GetSharedInstance();
  bundle.ReloadLocaleResources(locale);
  bundle.AddDataPackFromPath(pak_dir.Append(FILE_PATH_LITERAL("resources.pak")),
                             ui::SCALE_FACTOR_NONE);
#if BUILDFLAG(ENABLE_PDF_VIEWER)
  NOTIMPLEMENTED()
      << "Hi, whoever's fixing PDF support! Thanks! The pdf "
         "viewer resources haven't been ported over to the GN build yet, so "
         "you'll probably need to change this bit of code.";
  bundle.AddDataPackFromPath(
      pak_dir.Append(FILE_PATH_LITERAL("pdf_viewer_resources.pak")),
      ui::GetSupportedScaleFactors()[0]);
#endif  
}
AtomMainDelegate::AtomMainDelegate() {}