I've noticed something like this when having just applied the update on various test sites, but this seemed to have something to do having cleared cache, and it was really probably just that things hadn't loaded yet.Sometimes when I'm near the bottom of a page the nav bar disappears completely and won't reappear until I scroll about halfway back up the page.
I can't reproduce the issue you have reported. If you are able to and able to get a screencast of it, that would be very helpful.