Projectiles occasionally move in the wrong direction, what did I do wrong?

I've been having trouble with my game in that sometimes when a projectile fires it will go in a random direction instead of where my mouse is pointing.

Edit: The camera is forced in its position in the example of what's happening, I'm not sure if that changes anything.

This is the local script

mouseDown = false

local Mouse = game.Players.LocalPlayer:GetMouse()
	
Mouse.Button1Down:Connect(function()
	mouseDown = true
	local Char = game.Players.LocalPlayer.Character
	local trigger = Char:FindFirstChild("MouseDown")
	print(trigger)
	print(Char)
	repeat
		print("Mouse down")
		trigger:FireServer(Mouse.Hit.p)
		print("Trigger fired")
		wait()
	until mouseDown == false
end)
	
Mouse.Button1Up:Connect(function()
	mouseDown = false
end)

This is the server script

local event = script.Parent.MouseDown
local cd = .1
local waiting = false
print("event")
event.OnServerEvent:Connect(function(plr,pos)
	if not waiting then
		waiting = true
		local part = Instance.new("Part")
		part.Position = pos
		
		local proj = Instance.new("Part")
		proj.Size = Vector3.new(1,1,4)
		proj.BrickColor = BrickColor.new("Royal purple")
		proj.Material = "Neon"
		proj.CanCollide = false
		proj.Anchored = false
		proj.Position = script.Parent.HumanoidRootPart.Position
		
		local bf = Instance.new("BodyForce")
		bf.Force = Vector3.new(0, workspace.Gravity * proj:GetMass(), 0)
		bf.Parent = proj
		
		proj.CFrame = CFrame.new(script.Parent.HumanoidRootPart.Position,Vector3.new(part.Position.X,script.Parent.HumanoidRootPart.Position.Y,part.Position.Z))
		
		bf = Instance.new("BodyVelocity")
		bf.Velocity = proj.CFrame.lookVector * 50
		bf.Parent = proj
		
		game.Debris:AddItem(proj,2)
		
		proj.Parent = workspace
		wait(cd)
		waiting = false
	end
end)

This is what's happening.

Hmmm. Looking at it, I am almost certain it's a problem with networking.

Basically, in Roblox when an unanchored object gets close to a player, Roblox gives that player the responsibility of the object (to help drop some load of the server), that leads to lag, inconsistency in position and velocity (and perhaps some hacking) which may very well appear as you can see in the gif you sent.

The solution for that is SetNetworkOwner if you call this function from a BasePart which is not anchored (otherwise it will error) with a nil parameter, the server will never let a player take control of it thus no more hopping and stuff like that.

Here's a cool article about it: Network Ownership

I've managed to fix the issue through the help of this thread

I've only changed the local script significantly from the original

mouseDown = false

local UserInputService = game:GetService("UserInputService")
local camera = workspace.CurrentCamera

local Mouse = game.Players.LocalPlayer:GetMouse()
	
Mouse.Button1Down:Connect(function()
	mouseDown = true
	local Char = game.Players.LocalPlayer.Character
	local trigger = Char:FindFirstChild("MouseDown")
	print(trigger)
	print(Char)
	repeat
		print("Mouse down")
		print(Mouse.Hit.p)
		local v = UserInputService:GetMouseLocation()
		trigger:FireServer(test(v.X,v.Y))
		print("Trigger fired")
		wait()
	until mouseDown == false
end)
	
Mouse.Button1Up:Connect(function()
	mouseDown = false
end)

function test(x,y)
	local unitray = camera:ViewportPointToRay(x, y)
	local ray = Ray.new(unitray.Origin, unitray.Direction * 200)
	local target, position = workspace:FindPartOnRay(ray, game.Players.LocalPlayer.Character or nil)
	return position
end