Given I am creating a new multipe choice quesetion
And I set the "Question name" to "Example"
When I press "Blanks for 3 more choices"
And I follow "Site home"
Then I should see the form change checker
However I am navigated away from the page

We need to extend the check in lib/formslib.php::startForm() to add $this->isSubmitted(), i.e.

if ($this->is_dirty() }} $this->isSubmitted()) {

    $PAGE->requires->js_call_amd('core_form/changechecker', 'markFormAsDirtyById', [$formid]);

}

This will ensure that a form which was submitted, but rejected, is marked as dirty.