Why does my part leave plot area?

My "Part" does not snap on to the plot instead it only snaps to the baseplate

Here is the code:

local placementModule = require(game.ReplicatedStorage.Modules.PlacementModuleV2)

local remote = game.ReplicatedStorage.Events.PlaceObj

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()

local partBtn = script.Parent.MainFrame.TestSubject

local plot

game.ReplicatedStorage.Events.ClientPlot.OnClientEvent:Connect(function(pltNm)
	plot = workspace.Plots:FindFirstChild(pltNm)
	print(pltNm)
end)

script.Parent.MainFrame.TestSubject.MouseButton1Click:Connect(function()
	placementModule:new("TestSubject", game.ReplicatedStorage.Models, plot.Plot, plot.PlacedObjects, true, true)
end)

mouse.Button1Down:Connect(function()
	placementModule:Finish(remote)
end)

Thanks for the help!