Chris Steipp: 

Pretty reliable repo for me has been to run the editor_ve.feature test, and the second Scenario fails with the error almost every time.  Watch the browser as the test runs to see the red error message appear before the ON/OFF toggle switches back to OFF:

$ export MEDIAWIKI_URL=http://en.m.wikipedia.beta.wmflabs.org/wiki/
$ export MEDIAWIKI_USER=USER
$ export MEDIAWIKI_PASSWORD=PASSWORD

:~/MobileFrontend/tests/browser$ bundle exec cucumber features/editor_ve.feature 
@chrome @en.m.wikipedia.beta.wmflabs.org @firefox @login @test2.m.wikipedia.org
Feature: VisualEditor

  Background:                               # features/editor_ve.feature:4
    Given I am in alpha mode                # features/step_definitions/common_steps.rb:77
    And I am logged into the mobile website # features/step_definitions/common_steps.rb:10

  Scenario: Switch from VisualEditor to source editor               # features/editor_ve.feature:8
    Given I am on the "Selenium Edit Test" page                     # features/step_definitions/common_steps.rb:88
    And I click the edit button                                     # features/step_definitions/editor_steps.rb:7
    And I see the VisualEditor overlay                              # features/step_definitions/editor_ve_steps.rb:9
    And The VisualEditor overlay has an editor mode switcher button # features/step_definitions/editor_ve_steps.rb:29
    And I click the editor mode switcher button                     # features/step_definitions/editor_steps.rb:32
    When I click the source editor button                           # features/step_definitions/editor_steps.rb:36
    Then I see the wikitext editor overlay                          # features/step_definitions/editor_steps.rb:11

  Scenario: Ensure we load the correct section # features/editor_ve.feature:17
    Given I am in alpha mode                # features/step_definitions/common_steps.rb:77
      timed out after 5 seconds, waiting for {:class=>"mw-mf-settings-off", :tag_name=>"span"} to become present (Watir::Wait::TimeoutError)
      ./features/step_definitions/common_steps.rb:82:in `block (3 levels) in <top (required)>'
      ./features/step_definitions/common_steps.rb:81:in `block (2 levels) in <top (required)>'
      ./features/step_definitions/common_steps.rb:78:in `/^I am in alpha mode$/'
      features/editor_ve.feature:5:in `Given I am in alpha mode'