This case has been closed by-design, however the problem area has had some changes. Now, instead of an assert being thrown a more helpful error message is generated and rendering of the Skinned Mesh Renderer is aborted. This is because the internal state of the skinned mesh renderer needs to track to mesh assigned to it, if that internal state isn't update then it can cause GPU crashes on Metal API based devices. After mesh swap the component must be given a chance to resync it's internal state to prevent this, this is done as part of the normal Unity update flow and happen after all user update method have run.