Sorting of Planets when zoomed out is reversed

I'm experiencing a graphics bug during the camera tutorial.  When zoomed all the way out, the planet icons get Z-sorted in the wrong order. As you can see in the images below, Hypatia is closest to the camera, yet it is drawn behind Melanthios.  The bug seems to affects icons in groups by type of some sort, so for example, asteroid icons all sort incorrectly relative to each other, but asteroids that are farther away from the camera than a planet will correctly show up behind the planet icon. And the sun icon seems to go behind everything no matter what.