I have the same issue with WidgetAnimation / BindWidgetAnim.
As soon as I give a widget an animation, I can no longer use it anywhere, because every blueprint(layout) that uses the widget fails to save with this error.
It’s caused not by the animation itself, but by the UPROPERTY(meta = (BindWidgetAnim)), when I delete it, it works. But I can no longer access the animation with c++.