All lenses flare, the ones with the better coatings just do a good job of keeping better contrast. The amount of flare apparent is pretty much proportionate to the amount of contrast between the exposure and the light source. If it is high enough, you can get flare not just from lens elements, but from light coming back from the camera body, or the film. Lens flare can be anything from an over all fog, foggy blacks, or the familiar aperture shaped burn, or burns (depending on the elements). Other sorts can be totally random in appearance.
Since it is opposite from the point source, it sounds like some sort of flare, not a leak, but you should get those fixed.