Unsure of the root cause, but occasionally an NPE is thrown in the editor console because HandleDynamicsFrameComplete is called and stopwatch has not yet been created.
NullReferenceException: Object reference not set to an instance of an object
VRC.Dynamics.ContactManager.HandleDynamicsFrameComplete () (at <18f19c27e14b4ae6a2e430e7e9917e85>:0)
VRC.Dynamics.VRCAvatarDynamicsScheduler.FinalizeJob (System.Boolean force) (at <18f19c27e14b4ae6a2e430e7e9917e85>:0)
VRC.Dynamics.PhysBoneManager.LateUpdate () (at <18f19c27e14b4ae6a2e430e7e9917e85>:0)