In lessons, if you pull down the menu from then user icon in the upper right you can't close it.
I never found the cause, but a fix is in morpheus.scripts.min.js, in function toggleUserNav,
There's already dependency upon specific classes in that function, so I don't think this should be an issue.
While you're looking at it: this isn't a reasonable way to dismiss in a screen reader. The standard approach is to bind the ESC key to close the menu. But I think I'd also put a close button in the upper right of the box, as everything else in Sakai does.
In general I recommend using jquery dialogs rather than rolling your own.