Try this: Draw two partially overlapping extruded rectangles in top/plan view. Do a solid subtraction or a solid addition of these two objects. Switch to front view and then ungroup the object you created. Notice the selection handles are not where they should be. To deal with this, switch to any other view and the handles will be correct again. I consider this a bug and I hope Diehl Graphsoft will fix it soon. It's really difficult to deal with this problem as a drawing gets more complex. Also, in complex drawing there's a tendency for the ungrouped solid subtractions to become corrupt if their ungrouped resulting in a "failed solid subtraction".