Some objects (the one I know for sure is the 'Bag Fence (Long)' object from 'Units -> Empty -> Objects (Fortifications)') will become un-editable after you press the 'end' key to destroy them. Up until that point they work fine (as fine as anything else). Some objects (the ones that work correctly) have their icon update (from the yellow 'empty object' icon) to a gray icon to indicate they are destroyed and can still be manipulated and deleted. Some objects appear to just become broken.
This used to work fine for all objects a while ago (I'm not sure exactly the version number).