XP orbs do not display correctly in third-person front-view when looked from an angle

When a lot of XP orbs are orbiting around my avatar, their are displayed differently in the two third-person views. In the "rear" view, the orb always looks round, regardless of the view angle. The the "front" view however, the orbs look like as if they were displayed on a vertical plane and they will disappear if the avatar is looked from top or bottom (the attached picture show them from 45 deg).