title: Geckodriver suddenly stopped working after a while and log stopped generating
body: <p>Following is geckdriver log.</p>
  
  <pre><code>JavaScript warning: https://xxxxx, line 1: String.toLowerCase is deprecated; use String.prototype.toLowerCase instead
  1571180445730   Marionette  INFO    Stopped listening on port 56930
  [Child 11304, Chrome_ChildThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 11304, [Parent 15620, Gecko_IOThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 18764, Chrome_ChildThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 1876[Parent 15620, Gecko_IOThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 18528, Chrome_ChildThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 18521571193870646    mozrunner::runner   INFO    Running command: "C:\\Program Files\\Mozilla Firefox\\firefox.exe" "-marionette" "-foreground" "-no-remote" "-profile" "C:\\Users\\xxxxx\\AppData\\Local\\Temp\\rust_mozprofile.wefGvenxtjuS"
  1571193871155   addons.webextension.screenshots@mozilla.org WARN    Loading extension 'screenshots@mozilla.org': Reading manifest: Invalid host permission: resource://pdf.js/
  1571193871155   addons.webextension.screenshots@mozilla.org WARN    Loading extension 'screenshots@mozilla.org': Reading manifest: Invalid host permission: about:reader*
  1571193874489   Marionette  INFO    Listening on port 59485
  1571193874542   Marionette  WARN    TLS certificate errors will be ignored for this session
  JavaScript error: https://xxxxx, line 2: ReferenceError: $ is not defined
  console.error: BroadcastService: 
    receivedBroadcastMessage: handler for
    remote-settings/monitor_changes
    threw error:
    Message: Error: Polling for changes failed: NetworkError when attempting to fetch resource..
    Stack:
      remoteSettingsFunction/remoteSettings.pollChanges@resource://services-settings/remote-settings.js:750:13
  
  JavaScript warning: https://xxxxx, line 1: String.toLowerCase is deprecated; use String.prototype.toLowerCase instead
  1571195357820   Marionette  INFO    Stopped listening on port 59485
  [Parent 16976, Gecko_IOThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 19196, Chrome_ChildThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 15192, Chrome_ChildThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 1[Parent 16976, Gecko_IOThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 17100, Chrome_ChildThread] WARNING: pipe error: 109: file z:/build/build/src/ipc/chromium/src/chrome/common/ipc_channel_win.cc, line 346
  [Child 1
  </code></pre>
  
  <p>The log stopped generating here and geckodriver has no any action even I force to close Firefox browser.
  The testing script also cannot be terminated.</p>
  
  <p>For the most part, if I force to close browser, testing will be terminated and fail the test.</p>
  
  <p>How can I solve this problem?</p>
  
  <hr>
  
  <p>Below is my firefox settings:</p>
  
  <pre><code>    fp = webdriver.FirefoxProfile()
  
      fp.set_preference("dom.webnotifications.enabled", False)
      fp.set_preference("dom.push.enabled", False)
      fp.set_preference("app.update.auto", False)
      fp.set_preference("app.update.doorhanger", False)
      fp.set_preference("app.update.service.enabled", False)
      fp.set_preference("app.update.url", "https://do.not.update")
      fp.set_preference("app.update.checkInstallTime", False)
      fp.set_preference("app.update.silent", True)
      fp.set_preference("app.update.download.attempts", 0)
      fp.set_preference("browser.search.update", False)
      fp.set_preference("extensions.update.enabled", False)
      fp.set_preference("services.sync.prefs.sync.extensions.update.enabled", False)
      fp.set_preference("app.update.interval", 2592000)
      fp.set_preference("app.update.link.updateAvailableWhatsNew", "no-update-available-whats-new")
      fp.set_preference("app.update.link.updateManualWhatsNew", "no-update-manual-whats-new")
      fp.set_preference("browser.download.folderList", 2)
      fp.set_preference("browser.download.manager.showWhenStarting", False)
      fp.set_preference(downloadDIR, os.getcwd())
      fp.set_preference("browser.helperApps.alwaysAsk.force", False)
      fp.set_preference("browser.helperApps.neverAsk.saveToDisk", "text/plain,text/csv,text/html,application/octet-stream,application/force-download,application/pdf,application/binary,application/json,application/vnd.ms-excel,application/zip")
      fp.set_preference("pdfjs.disabled", True)
  
      self.driver = webdriver.Firefox(firefox_profile=fp)
  </code></pre>