Not sure if an object can be relink after he has been detached from an element. but i know if you link more then 2 objects with an ArchiCad element such as wall/roof/slab, when you'll link the third one, one of the 3 objects who are linked will loose the link. If make sense...
And so on, if you'll place more then 2 objects.
i noticed that 2 objects are fine, works fine.
Now this is not going to happen if you'll use the Cadimage accessory tool.
Try It!
Sincerely,
Daniel