I have Vertex 4.2.0 (installed it when it first came available) and just noticed that the main menu stopped working correctly; sub-menus will no longer display, just the primary menu.
Using Joomla 3.8.6 with the Helion template (which I've used for over four years).
Also using PHP Version 7.0.28.
www.drummercafe.comI will continue to investigate on my own to see if I can resolve it... then will report back.