When you set your application to not collapse the sidebar menu by default, it does not work properly if you start with a fresh navigator session because this option is missing until you click the collapse or expand menu icon for the very first time. If you start with local session storage settings empty, you will see that nav.200.preferenceForExpanded is completely missing.
If you do not press it the very first time and you start jumping between pages, you will see that the screen flickers and the menu opens on every page load.