Why wont this work?

So I am trying to build a elevator, and for some reason. I have the script in ServerScriptService. When it goes down, It can't go back up My Script:

local model = game.Workspace.Elevator
local platform = model.Platform
local top = model.Top
local bottom = model.Bottom
local bodyPosition = platform.BodyPosition

while true do
bodyPosition.position = bottom.Position
wait(6)
bodyPosition.position = top.Position
wait(6)
end

When I am in studio It shows no errors. To see what I have for the Elevator go here: http://web.roblox.com/Testing-Area-place?id=174590350