How do I fix this fall damage script?

[Wyzloc]

This fall damage script works, but not all the time. What’s wrong with it?

local lastYPos = {}
function connectFallDamage(Char)
	local Humanoid = Char:FindFirstChild("Humanoid")
	local InAir = false
	Humanoid.StateChanged:Connect(function(old, new)
		print(old, new)
		if new == Enum.HumanoidStateType.Freefall then
			if lastYPos[Char] then return end
			local Root = Char:FindFirstChild("HumanoidRootPart")
			if Root then
				lastYPos[Char] = Root.Position.Y
				print(lastYPos[Char].." Falling")
			end
		elseif old == Enum.HumanoidStateType.Freefall and new == Enum.HumanoidStateType.Landed and lastYPos[Char] then
			local Root = Char:FindFirstChild("HumanoidRootPart")
			if Root then
				if lastYPos[Char] > Root.Position.Y then
					local Dmg = (lastYPos[Char] - Root.Position.Y)/2
					local health = game.ServerStorage.CharacterHealths:FindFirstChild(Char.Name.."Health")
					if health then
						if health.Value - Dmg <= 0 then
							health.Value = 1
							Event:Fire(Char, 15, true)
						else
							health.Value = health.Value - Dmg
						end
					end
				end
			end
			lastYPos[Char] = nil
		end
	end)
end