Scroll wheel tool change broken, can someone help?

Can someone tell me whats wrong with this fix and possibly fix it. I did not make this script btw but I really need it to work. It's supposed to cycle through tools with use of scroll wheel. The forward wheel works with switching weapons, but the scrollwheel back unequips all tools and doesn't equip a new one.

local player = game.Players.LocalPlayer
local char = player.Character or player.CharacterAdded:wait()
game:GetService("UserInputService").InputChanged:connect(function(iO,gPE)
	if not gPE then
		if iO.UserInputType == Enum.UserInputType.MouseWheel then
			print(iO.Position.Z)
			local LastTool = nil
			local Pos = 1
			for i,v in pairs(char:GetChildren())do
				if v:IsA'Tool'then
					LastTool = v
				end
			end
			char.Humanoid:UnequipTools()
			for i,v in pairs(player.Backpack:GetChildren())do
				if v==LastTool then
					Pos = i
				end
			end
			if iO.Position.Z == 1 then
				if Pos == 1 then
					Pos = #player.Backpack:GetChildren()
					char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
					wait()
				else
					Pos = Pos-1
					char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
					wait()
				end
			elseif iO.Position == -1 then
				if Pos == #player.Backpack:GetChildren() then
					Pos = 1
					char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
					wait()
				else
					Pos = Pos+1
					char.Humanoid:EquipTool(player.Backpack:GetChildren()[Pos])
					wait()
				end
			end
		end
	end
end)