Why wont this script work? (URGENT) places blocks on the front top and rights sides of a block

This script is meant to place blocks on a 3d grid by rounding. BUT it only works on the top right and front Faces. ANY other faces will result in it placing the block inside the original.

local Mouse = game.Players.LocalPlayer:GetMouse()
local Positiona
local bloc
local pos
local X
local Y
local Z
local lasserx
local lassery
local lasserz

script.Parent.Activated:Connect(function()
	
	script.Parent.place:FireServer(Positiona, bloc, pos)
	bloc = script.Parent:GetAttribute("block")
	pos = Mouse.Target
end)

Mouse.Move:Connect(function() -- NEW PLACEMENT SYSTEM
	local GridSize = 4
	if Mouse.TargetSurface.Name == "Top" or "Right" or "Front" then
		 X = math.floor((Mouse.Hit.X + GridSize / 2) / GridSize) * GridSize
		 Y = math.ceil((Mouse.Hit.Y + GridSize / 4 ) / GridSize) * GridSize - 1.5
		Z = math.floor((Mouse.Hit.Z + GridSize / 2) / GridSize) * GridSize
		lasserx = false
		lassery = false
		lasserz = false
	elseif Mouse.TargetSurface.Name == "Bottom" then
		X = math.floor((Mouse.Hit.X + GridSize / 2) / GridSize) * GridSize
		Y = math.ceil((Mouse.Hit.Y + GridSize / 4 ) / GridSize) * GridSize - 1.5
		Z = math.floor((Mouse.Hit.Z + GridSize / 2) / GridSize) * GridSize
		lasserx = false
		lassery = true
		lasserz = false
	elseif Mouse.TargetSurface.Name == "Left" then
		X = math.floor((Mouse.Hit.X + GridSize / 2) / GridSize) * GridSize
		Y = math.ceil((Mouse.Hit.Y + GridSize / 4 ) / GridSize) * GridSize - 1.5
		Z = math.floor((Mouse.Hit.Z + GridSize / 2) / GridSize) * GridSize
		lasserx = true
		lassery = false
		lasserz = false
	elseif Mouse.TargetSurface.Name == "Back" then
		X = math.floor((Mouse.Hit.X + GridSize / 2) / GridSize) * GridSize
		Y = math.ceil((Mouse.Hit.Y + GridSize / 4 ) / GridSize) * GridSize - 1.5
		Z = math.floor((Mouse.Hit.Z + GridSize / 2) / GridSize) * GridSize
		lasserx = false
		lassery = false
		lasserz = true
	end
	
	if lasserx == true then
		Positiona = CFrame.new(X - 1, Y, Z)
	elseif lassery == true then
		Positiona = CFrame.new(X, Y - 1, Z)
	elseif lasserz == true then
		Positiona = CFrame.new(X, Y, Z - 1)
	else
		Positiona = CFrame.new(X, Y, Z)
		end

end)