Why do the part just move downwards?

i want to make a part that moves the direction the mouse is, but there is some problems.

The problem is that the part just moves downwards really glitchy and just stops at Y -65
And then it starts to move forward and works as it should

I have asked on the roblox discord but they told me to go here instead. I have tried disabling the script that makes the part move and then it wont move downwards.

The part is anchored.

Here is the script that makes it rotate

Move.OnServerEvent:Connect(function(plr, Orientation)
	local Snake = workspace["SnakeHead_"..plr.Name]
	Snake.CFrame = CFrame.new(Snake.Position, Orientation)
	Snake.Orientation = Vector3.new(0, Snake.Orientation.Y, 0)
	--Snake.CustomPhysicalProperties = physProperties

Here is the script that moves it

while true do
	script.Parent.CFrame = script.Parent.CFrame*CFrame.new(0,0,-0.5)

oh wait, i fixed it. It was just that the part in the beginning was facing -90 in rotation. That caused some it to move downwards in the beginning