Well, I ran into a huge problem with my map today. When I tried to add the last few pieces to my map, the lighting goes all wonky. After trying for hours to fix it, I looked it up online. Turns out its a common glitch. There is a hidden 'dynamic lighting budget' in forge. Someone went through all the trouble of testing out each piece and gave them a value on how much of your budget it takes up. So try to use the least expensive items when forging.
Here is link to post on Forgehub.
http://www.forgehub.com/forum/halo-4-fo ... hting.html