The icons in the palette are only templates for the visual appearance of nodes and edges. They do not determine the connection behavior of elements at all. However, normal nodes and group nodes have slightly different connection behavior. For normal nodes, it is possible to start edge creation anywhere inside a node. For group nodes, it is possible to start edge creation only close to the node border (farther inside will start marquee selection). Maybe the problematic templates are group node templates? Unfortunately, with the little information at hand it is impossible to provide more specific advice. For more advice, please export the relevant palette section (see "Edit" -> "Manage Palette") and upload the corresponding palette section GraphML file here.
