... Maybe this is just a rare issue resulting from doing updates and not clean installs, little things falling through the cracks during the update process.
Regarding the Cortana icon, it is unlikely that this is just falling through the cracks, @hughlle . Below is a screen shot I just now took of my MacBook Pro Retina 15 under the same Build, installed directly, not from updates.
By the way, Windows 10 works very well with my MacBook (via Parallels 10). And if I change the desktop background on my Surface Pro 3, the MacBook changes within 30 seconds or so. And vice versa.
MacBook Pro Retina 15 inch