I have had similar problems, and currently have a support request open (1-2558535661) that was submitted on 10/12/2007, so it
appears that it is a difficult problem to resolve.
One suggestion: to make a repeatable instance, just mock up an island vent, where the vent pipe comes up vertically, then uses 45
deg/90 deg/45 deg pipe and fittings to go back down vertically. This arrangement is always unmovable in either the "x" or "y"
direction, depending on the orientation of the angled pipes. To sum it up, if the pipes are drawn in the "x" direction, they won't
move in the "x" direction, but will move in the "y" direction.
I also had trouble mirroring pipes from one unit to another, but found that if you group them first you will have much better luck.
John
wrote in message news:5981850@discussion.autodesk.com...
I've seen this issue too, but haven't been able to isolate the cause (or even find a reliable repeatable case)... please contact
product support, and please provide the dataset.