When the Gladers were in the Glade in The Maze Runner and the lift came up carrying supplies and even another Glader, why couldn't the Gladers jump inside of the lift in order to escape? It would take them down to the lab where they came from.
They actually tried that, but it is stated that the elevator would not go down when someone was in it. Thomas at one time starts inquiring about the possibility of doing just that.
And what about the Box? Next time it comes up...
Here he's cut in mid sentence and Newt replies.
No, we tried that. The Box won't go back down with someone in it.
Apparently Chancellor Ava Paige and the rest of her crew were watching if the gladers attempted to exploit this specific loop hole. You could find this conversation around the 20 minute mark of the movie.
They tried that. The lift wouldn't physically go down with weight in it. Also they tried with a hand made rope but weren't able to make it long enough. On another attempt to get down, a guy was asumed to have gone to his death by falling although the people at the top did not hear him land because of long way down. This happened after him trying to climb down. They all gave up after that