Setting capabilities specifying a firefox version or a selenium version by default breaks when running against a server being strict about the requested capabilities (as it is unlikely to run Firefox 9 these days).
Note that I faced this issue when trying to run tests against geckodriver (as it is strict about respecting the Firefox version, unlike the old FirefoxDriver of Selenium 2).
Setting capabilities specifying a firefox version or a selenium version by default breaks when running against a server being strict about the requested capabilities (as it is unlikely to run Firefox 9 these days). Note that I faced this issue when trying to run tests against geckodriver (as it is strict about respecting the Firefox version, unlike the old FirefoxDriver of Selenium 2).