Random BodyGyro twitching?

I'm trying to create a local script for flying, and I'm using a BodyGyro to bend the character forward. This makes the character twitch, and I have no idea why.

player = game.Players.LocalPlayer
repeat wait() until player.Character
character = player.Character
torso = character:WaitForChild("Torso")
humanoid = character:WaitForChild("Humanoid")

UIS = game:GetService("UserInputService")

space_presses = 0
press1 = 0
press2 = 0
flying = false
w_down = false

bpos = Instance.new("BodyPosition")
bpos.MaxForce = Vector3.new(math.huge, math.huge, math.huge)

bgyro = Instance.new("BodyGyro") 
bgyro.MaxTorque = Vector3.new(math.huge, math.huge, math.huge)

UIS.InputBegan:connect(function(input)
    if input.KeyCode == Enum.KeyCode.Space then
        space_presses = math.min(space_presses + 1, 2)
        if space_presses == 1 then
            press1 = tick()
        elseif space_presses == 2 then
            press2 = tick()
            if press2 - press1 > .3 then
                space_presses = 1
                press1 = tick()
            else
                space_presses = 0
                flying = not flying
                if flying then --When you double jump
                    bpos.Position = torso.Position
                    bpos.Parent = torso --Start flying
                else --When you do another double jump
                    bpos.Parent = nil --Stop flying
                    w_down = false
                end
            end
        end
    elseif input.KeyCode == Enum.KeyCode.W then --When you press W
        w_down = true
        bgyro.Parent = torso
        while w_down and wait() do --And you hold it
            bpos.Position = torso.Position + workspace.Camera.CFrame.lookVector * 10 --Move forward
            bgyro.CFrame = CFrame.new(torso.Position, torso.Position + workspace.CurrentCamera.CFrame.lookVector * 10) * CFrame.Angles(-math.pi/2, 0, 0) --And bend forward 90 degrees
        end
    end
end)

UIS.InputEnded:connect(function(input)
    if input == Enum.KeyCode.W then --When you let go of W
        w_down = false --Break the loop
    end
end)