If there are several objects where you use the skill, only the first to have been spawned is deleted.
In defilante maps, the place where you have to use a skill to delete an object may be different than the object's original place.
If several objects are bound by a red nail and if you delete the first one to have been spawned, the remaining objects are not fixed. (This problem is that only the object that you delete is attached.)
If several objects are bound by a red nail, one that is more in the background can not be deleted. (V1.161)
If several objects are bound by a blue nail, only the one who is most in the background can be deleted. (V1.161)