Selenium::WebDriver::Error::UnknownError: invalid argument: can't kill an exited process | Travis webdrivers

I try to build on Travis and launch my user test but I have the following error : Selenium::WebDriver::Error::UnknownError:invalid argument: can't kill an exited process I may use wrong version of firefox and geckodriver but can't figure out what is the right one.. Here is the screenshot of travis interface and my travis.yml file. Thanks a lot !

language: ruby
cache:
  bundler: true
  yarn: true
  directories:
  - vendor/bundle
  - node_modules
  - tmp/cache
  - public/assets
services:
  - redis-server
sudo: required
addons:
  postgresql: '9.5'
  chrome: stable
  firefox: latest
  apt:
    packages:
      - chromium-chromedriver
      - google-chrome-stable

before_install:
  - gem install bundler -v 2.0.1
  - openssl aes-256-cbc -K $encrypted_67af5a301080_key -iv $encrypted_67af5a301080_iv
    -in application.yml.enc -out config/application.yml -d
  - sudo apt-get update
  - sudo apt-get install google-chrome-stable
  - wget https://github.com/mozilla/geckodriver/releases/download/v0.24.0/geckodriver-v0.24.0-linux64.tar.gz
  - mkdir geckodriver
  - tar -xzf geckodriver-v0.24.0-linux64.tar.gz -C geckodriver
before_script:
  - psql -c 'create database simundia_v6_test;' -U postgres
script:
  - bundle exec rake db:migrate
  - yarn install --production=false
  - bundle exec rails assets:precompile
  - bundle exec rspec $TESTFOLDER
env:
  - TESTFOLDER=spec/features/coach_journey_spec.rb
  - TESTFOLDER=spec/features/coached_journey_spec.rb
  - TESTFOLDER=spec/features/client_demo_journey_spec.rb
  - MOZ_HEADLESS=1

10.87s$ bundle exec rspec $TESTFOLDER
Capybara starting Puma...
* Version 3.12.0 , codename: Llamas in Pajamas
* Min threads: 0, max threads: 4
* Listening on tcp://127.0.0.1:43817
F
Failures:
  1) Coach user journey success
     Failure/Error: visit '/users/sign_in'
     Selenium::WebDriver::Error::UnknownError:
       invalid argument: can't kill an exited process
     # ./spec/features/utilities.rb:18:in `visit_session_new'
     # ./spec/features/coach_journey_spec.rb:17:in `block (2 levels) in <top (required)>'