Main menu collapses when accessing sub menus

The left-hand main menu contains several main and sub items. Whenever a sub item is clicked and the page is reloaded, the new page does not expand the relevant menu item. This causes the user to loose track of where he/she was.

This specifically occurs for the People menu item, with sub items such as 'My Population', 'Enroll' and 'CO Petitions'. If one of those sub items is selected, the People menu seemingly collapses (page is reloaded, menu is not expanded).