In Halo 3 Custom Games, why can't I put the bomb down?

I made a map myself on Sandbox meant for the Assault game, One Bomb. The Attackers are in the sky in a small base, and the Defenders are on the ground. In Custom Games, when I bring the bomb down and walk to the detonation place, the waypoint is there, but the bomb stays in my hands. Also, there's a bomb spawning point randomly on the map. I deleted it and saved changes but when I start a match, it is there. How do I fix these problems? Help?