Everytime I try to insert a dimple that I have created on to a surface of a sheet metal part, the program is asking me if I am trying to make a derived part.  If I choose no, it opens the dimple that I have drawn.  If I choose yes, it wants me to place it into my part as another part instead of a form tool.  Some of my form tools are working correctly and others are giving me the same error.  What could be causing such an error?