The control scripts are setting MouseBehavior back, so to stop that you will need to set it every frame.
local RunService = game:GetService"RunService"
local UserInputService = game:GetService"UserInputService"
RunService:BindToRenderStep("MouseLock",Enum.RenderPriority.Last.Value+1,function()
UserInputService.MouseBehavior = Enum.MouseBehavior.LockCenter
end)