Model lightmapping issue

I've ran into a certain weird problem with lightmaps on my props. Whenever I turn them by non-90-degree angle (5 degress, 15, 60, etc.), pitch-black areas appear on those as shown on the screenshot. The leftmost and rightmost panels are turned by 0 and 90 degrees, while others were rotated by arbitrary angles. Even a puny angle of 1 degree gives this effect. I don't know if some bug in q3map2 is the reason, or there's something wrong with my props. I tried changing many shader parameters, using raw textures, compiling map with different configurations yet it all was in vain. Does anyone have an idea about the cause of this?
Here's the prop itself - http://ompldr.org/vOTB2ZA/hexpanel.zip

Oh well. Seems like q3map2 does it wrong when mesh is rotated by an arbitrary angle and there are two or more close standing parallel planes - they begin to project pitch-black shadows on each other. I deleted back sides of those panels and everything works fine now.