Sketch Feature should not be connected to Definition Collection.
A sketch feature is a special type of symbol that should not be related to the Definition Collection. This relationship is for low level internal use by the software and is not visible to the user.
If you split a plate system (and parts on it) by a design seam, the design seam splits a sketched feature so that it appears on more than one part. Some versions of Smart 3D can create this improper relationship. The root cause of this problem is fixed in version 2016; however, you can encounter this problem in earlier versions of Smart 3D.
Some copy operations will fail if the software encounters an improper relationship. You can copy parts using the normal procedure to correct the problem and also perform the steps listed below.
What You Should Do
Ask your database administrator to back up the model.
Open the model.
Run the Clean Database custom command.
Select the check box for the sketch feature you want to fix, and then click Clean Now.