Insert this code into a LocalScript inside StarterCharacter:
task.wait(1)
local UserInputService = game:GetService("UserInputService")
local Camera = Workspace.CurrentCamera
UserInputService.MouseBehavior = Enum.MouseBehavior.LockCenter
Then hold the right mouse button down, and start moving the mouse while rapidly left clicking.
Expected behaviour: The mouse cursor remains locked exactly in the center of the screen.
Actual behaviour: Mouse cursor flickers and will move to the right and back.
Platform: Windows 10