Hi there
We have the essentials theme installed on one of our clients Moodle 25 installs and we noticed a bug with the navigation header. When you click on a navigation link it appears that the drop down does not render. However, if you then click on another navigation link the drop down for the old link appears.

From my limited testing it looks like it's possible that the drop down open class is being applied to the last clicked navigation list item, instead of the current one.

I'm using Ubuntu 13.04 and Firefox 20.0