How do I prevent a scriptable camera from being laggy? Please Help

So I've been working on a game where you control a ball, and I've had a serious problem for several months now. I've been ignoring it so I can finish the overall gameplay for the game, but now that I'm done with the gameplay I can't continue because of this.

Script for ball movement:

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()
local left = false
local right = false
local up = false
local down = false
local bVel = nil
local rDown = false
local xVel = 0
local zVel = 0
local functions = require(Workspace.CoreFunctions)
local runService = game:GetService("RunService")


--Don't call "Enum.KeyCode" everytime a key is pressed
local keyCode = Enum.KeyCode

--[[       0.1 - 0.5 = Heavy Friction;     0.5 - 0.9 Low Friction]]
local friction = .9
game.StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Health, false)
game.StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Backpack, false)
--game.StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.PlayerList, false)
game.StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.Chat, false)
--game.StarterGui:SetCore("TopbarEnabled",true)
local keys = game:GetService("UserInputService")
local step = game:GetService("RunService")

--[[
player.CharacterAdded:connect(function()
    wait()
    player.Character:WaitForChild("Torso").Anchored = true
    --player.Character.Parent = game.Lighting
    for i,v in pairs(game.Workspace:GetChildren())do
        if v.Name == "Ball" then
            if v:FindFirstChild('Owner') then
                if v.Owner.Value == player.Name then
                    ball = v
                    bVel = ball.BodyVelocity
                end
            end
        end
    end
end)
]]

wait(.5)
local ball = functions.findBall(player)


keys.InputBegan:connect(function(key)
    if player.PlayerGui.ChatHolder.ChatBar.Visible == false and player.PlayerGui.Spectating.Value == false then
        k = key.KeyCode
        if k == keyCode.Left or k == keyCode.A then
        left = true


        elseif k == keyCode.Right or k == keyCode.D then
            right = true


        elseif k == keyCode.Up or k == keyCode.W then
            up = true


        elseif k == keyCode.Down or k == keyCode.S then
            down = true
        end
    end
end)


keys.InputEnded:connect(function(key)
    k = key.KeyCode
    keyDown = false
    if k == keyCode.Left or k == keyCode.A then
        left = false


    elseif k == keyCode.Right or k == keyCode.D then
        right = false


    elseif k == keyCode.Up or k == keyCode.W then
        up = false


    elseif k == keyCode.Down or k == keyCode.S then
        down = false
    end
end)



while ball == nil do
    wait()
end





function onRenderStep()
    xVel = xVel * friction
    zVel = zVel * friction
    ball.BodyVelocity.velocity = Vector3.new(xVel,0,zVel)

        if left then
            zVel = zVel - 5
        end

        if right then
            zVel = zVel + 5
        end

        if up then
            xVel = xVel + 5
        end

        if down then
            xVel = xVel - 5
        end

end

runService:BindToRenderStep("Controls",Enum.RenderPriority.Camera.Value, onRenderStep)

Script for camera movement:

local player = game.Players.LocalPlayer
--local ball = nil
local functions = require(Workspace.CoreFunctions)
local specBall = nil
local runService = game:GetService("RunService")
--[[
player.CharacterAdded:connect(function()
    wait()
    for i,v in pairs(game.Workspace:GetChildren())do
        if v.Name == "Ball" then
            if v:FindFirstChild('Owner') then
                if v.Owner.Value == player.Name then
                    ball = v
                end
            end
        end
    end 
end)
]]

wait(.5)
local ball = functions.findBall(player)
local pos = nil

while ball == nil do
    wait()
end


local cam = game.Workspace.CurrentCamera
cam.CameraType = "Scriptable"
--Camera subject is useless here
--cam.CameraSubject = ball
cam.CoordinateFrame = CFrame.new(ball.Position + Vector3.new(0,50,0))
local target = script:WaitForChild("CamTarget")



--[[
runService.RenderStepped:connect(function()
    if target.Value == "ball" then
        local campos = cam.CoordinateFrame.p:Lerp(ball.Position + Vector3.new(0,50,0),0.10)
        cam.CoordinateFrame = CFrame.new(campos,ball.Position)
    elseif target.Value ~= "ball" then
        if specBall == nil then
            specBall = functions.findBall(game.Players:FindFirstChild(target.Value))
        end
        cam:Interpolate(specBall.CFrame*CFrame.Angles(12,210,31),specBall.CFrame, .3)
        cam.CoordinateFrame = CFrame.new(specBall.Position + Vector3.new(0,50,0))
    end
end)
]]

local offset = Vector3.new(0,50,0)

function onRenderStep()
    if target.Value == "ball" then
        --[[
        pos = CFrame.new(ball.Position) + Vector3.new(0,50,0)
        cam:Interpolate(ball.CFrame, ball.CFrame,.2)
        cam.CoordinateFrame = pos
        ]]

        local ballPos = ball.Position
        local camPos = (ballPos) + offset
        cam.CoordinateFrame = CFrame.new(camPos,ballPos)


    elseif target.Value ~= "ball" then
        if specBall == nil then
            specBall = functions.findBall(game.Players:FindFirstChild(target.Value))
        end
        cam:Interpolate(specBall.CFrame*CFrame.Angles(12,210,31),specBall.CFrame, .3)
        cam.CoordinateFrame = CFrame.new(specBall.Position + Vector3.new(0,50,0))
    end
end

runService:BindToRenderStep("Camera",Enum.RenderPriority.Camera.Value, onRenderStep)

As you can see in the scripts I'm using RenderStepped for the movement, and HeartBeat for the camera(The camera won't interpolate correctly with RenderStepped). The camera will run smoothly if you're by yourself(about 80% of the time) but if you are playing with someone else and you get near them during the "match" the lag skyrockets. If you can't tell why this is happening based on the code can you at least tell me why you think this might be happening. I'm very desperate and will take any and all advice right now. The kind of lag that happens is sort of "input lag", where when you press down on a key the response is a little slower, and at the same time there is what I think is camera movement lag. The camera starts to be slightly behind the ball and kind of bounces.

Here's the place: Freeze Tag

tl:dr PLEASE HELP ME WITH THIS. I AM SO DESPERATE

This was edited on 3/10/16