Why is my NPC interacting with a non-collidable object?

I have a npc that follows you around. I want to create a cylinder at certain intervals that is attached to the npc. When I try to do this, my boss interacts with my cylinder for a quarter of a second when canCollide is clearly disabled. The same thing happened to me when I imported a cylinder from blender and tried using that. However, any use of a plain "MeshPart" seems to not affect the npc. These two interactions only happen when I have my weld that welds between the new part and the npc. Here is the code that I am using:

local warning = Instance.new("Part")
warning.CanCollide = false
warning.Anchored = false

local mesh = Instance.new("SpecialMesh")
mesh.MeshType = Enum.MeshType.Cylinder
mesh.Parent = warning

warning.Size = Vector3.new(16, .1, 16)
warning.CFrame = CFrame.new(myChar.HumanoidRootPart.Position.X, 4, myChar.HumanoidRootPart.Position.Z)

warning.Name = "Warning"

warning.Parent = game.workspace
local weld = Instance.new("WeldConstraint")
weld.Part0 = myChar.Head
weld.Part1 = warning
weld.Parent = warning

warning:SetNetworkOwner()