The issue stems from the new moveable ui and taint. Previously taint issues were not as much of an issue since a it really mattered with a few ui elements. Now since the ui mover affects a bunch of frames, if any of them becomes tainted the UI mover becomes tainted and then taints all the moveable frames, which causes the game to start throwing out endless errors. Addon authors are going to have to really rework things to limit taint issues but there is only so much that an be done.