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)