Upgrade to 4.2.1 was recently done for NXP-10821, but it seems upgrading to 4.2.3 could solve other test issues (see NXS-1473)
NXS-1473 Fix launching of webdriver tests with FF 19
NXP-10821 Avoid use of shaded selenium-server-standalone
NXP-11125 Upgrade to Selenium 2.31.0 for compliance with FF 19