Gear keeps glitching out?

I have inserted the "US Military Top Secret Experimental Jetpack" gear from the catalog into the StarterGear but when I am flying in the air, my character turns to the left or right and then glitches out and he keeps turning left to right real quickly. There is an animation called "standstill". I will post parts of the code since there is over 200 lines.

Here is the first part of it:

local Tool = script.Parent

--print(Tool)

--while Tool == nil do
--  Tool = script.Parent
--  wait(.5)
--end

local mass = 0
local player = nil
local equalizingForce = 236 / 1.2 -- amount of force required to levitate a mass
local gravity = .75 -- things float at > 1
local moving = false

local maxFuel = 1000

while Tool == nil do
    Tool = script.Parent
    wait(.5)
end

local currfuel = Tool:FindFirstChild("CurrFuel")
while currfuel == nil do
    Tool = script.Parent
    currfuel = Tool:FindFirstChild("CurrFuel")
    wait(.5)
end

local fuel = Tool.CurrFuel.Value

local gui = nil

local anim = nil

local jetPack = nil

local regen = false

Here is when it first has the animation:

function onEquippedLocal(mouse)

    player = Tool.Parent
    while player.Name == "Backpack" do
        player = Tool.Parent
        wait(.5)
    end

    equipPack()
    mass = recursiveGetLift(player)
    force.P = mass * 10
    force.maxForce = Vector3.new(0,force.P,0)
    mouse.Button1Down:connect(thrust)
    mouse.Button1Up:connect(cutEngine)
    cam = game.Workspace.CurrentCamera
    anim = player.Humanoid:LoadAnimation(Tool.standstill)
    anim:Play()
    gui = Tool.FuelGui:clone()
    updateGUI()
    gui.Parent = game.Players:GetPlayerFromCharacter(player).PlayerGui

    regen = true
    regenFuel()

end