1. If you don't anchor some side then it will stay in place where it was left -- meaning it will behave as if it's anchored to the parent. If you want the widget to stay the same size, then you should anchor all sides to the same values (left to left, right to left, bottom to top, top to top for example).
2. Run time or edit time? If it's edit time then that might be a minor bug that needs to be fixed.