autocomplete regularly fails with stale elements

002 Scenario: Adding a user to multiple groups               # /var/www/html/moodle/enrol/tests/behat/add_to_group.feature:26

      And I click on "Group 2" item in the autocomplete list # /var/www/html/moodle/enrol/tests/behat/add_to_group.feature:34

        WebDriver\Exception\StaleElementReference: stale element reference: element is not attached to the page document

          (Session info: chrome=61.0.3163.100)

          (Driver info: chromedriver=2.33.506092 (733a02544d189eeb751fe0d7ddca79a0ee28cce4),platform=Linux 4.4.0-97-generic x86_64) in /var/www/html/moodle/vendor/instaclick/php-webdriver/lib/WebDriver/Exception.php:155

        Stack trace:

        #0 /var/www/html/moodle/vendor/instaclick/php-webdriver/lib/WebDriver/AbstractWebDriver.php(157): WebDriver\Exception::factory(10, 'stale element r...')