[PATHFINDING] My NPC is bugging out with runService.Stepped?

local npc = script.Parent
local head = npc:FindFirstChild("Head")
local debris = game:GetService("Debris")
local screamSound = head:FindFirstChild("ScreamSound")
local Zone = require(game.ReplicatedStorage.Zone)
local playersInZone = require(game.ServerScriptService.PlayersInZone3Script)
local container = workspace:FindFirstChild("RegionPart3")
local zone = Zone.new(container)
local npcTorso = npc:FindFirstChild("Torso")
local pathfindingService = game:GetService("PathfindingService")
local quickSlash = npc.Swing
local quickSlashAnimTrack = npc.Humanoid:LoadAnimation(quickSlash)
quickSlashAnimTrack.Priority = Enum.AnimationPriority.Action
local properties = {["WaypointSpacing"] = 1.1,
	["AgentRadius"] = 2.5
}
local runService = game:GetService("RunService")


function getClosestPlayer()
	local closestPlayer, closestDistance = nil, 200
	for i,char in pairs(workspace:GetChildren()) do
		if char:FindFirstChild("Humanoid") and char ~= npc then
			local hmr = char:FindFirstChild("HumanoidRootPart")
			if hmr then
				local distance = (npcTorso.Position - char.HumanoidRootPart.Position).Magnitude
				if distance < closestDistance then
					closestPlayer = char
					closestDistance = distance
				end
			end
		end
	end
	return closestPlayer, closestDistance
end

function moveNPC()
	local path = pathfindingService:CreatePath(properties)
	local char, distance = getClosestPlayer()
	if char then
		path:ComputeAsync(npc.HumanoidRootPart.Position,char.PrimaryPart.Position)
		if (npc.HumanoidRootPart.Position - char.HumanoidRootPart.Position).Magnitude >20 and (npc.HumanoidRootPart.Position - char.HumanoidRootPart.Position).Magnitude >22 then
			screamSound:Play()
		end
		local waypoints = path:GetWaypoints()
		for i, waypoint in pairs(waypoints) do
			local part = Instance.new("Part")
			part.Size = Vector3.new(1,1,1)
			part.Transparency = 0.7
			part.CanCollide = false
			part.Position = waypoint.Position
			part.Parent = workspace
			debris:AddItem(part,.5)
			if (npc.HumanoidRootPart.Position - char.HumanoidRootPart.Position).Magnitude > 2.2 then
				npc.Humanoid:MoveTo(waypoint.Position)
			end
			while true do
				local distance = (npc.HumanoidRootPart.Position - waypoint.Position).Magnitude
				if distance < 5 then
					break
				end
			wait()
			end
			
		end
	end
end

--[[zone.playerEntered:Connect(function(player)
	table.insert(playersInZone,player)
	print(player.Name.." entered zone 3")
end)

zone.playerExited:Connect(function(player)
	local playerFound = table.find(playersInZone,player)
	wait(0.5)
	table.remove(playersInZone,player)
	print(player.Name.." exited zone 3")
end)--]]

while wait() do
	--for i,player in pairs(playersInZone) do
	--	if i == 1 then
			runService.Stepped:Connect(moveNPC)
		--end
	--end
end

https://i.gyazo.com/cf2e7eca61d5f5f6f99e6ec9d615e889.mp4

So the NPC is walking towards the closest humanoid in a maze, however he seems to be bugging out (refer to gyazo link). I notice this only when I use runService.Stepped. If I just use a while loop, it doesn't happen however it doesn't follow the character smoothly, so I want to use runService. It seems to be moving back on itself, like as it it's trying to move to a previous waypoint for a split second. Anyway, if anyone can help I'd appreciate