I was mapping for the 2016 spawnroom contest. I created a window as seen in the video, but when I fired an arrow at the right window, the left window turned black/dark. The glass material is glass/glasswindow001a on the other side and icarus/glasschrome003 on the other side. I checked, there were no problems with the map or any leaks. Is this a common problem? Will it continue happening if I add lights, finish detailing... ? If you can help me, thank you.