The location and type of stucco crack may provide some insight into if the stucco is installed correctly. But not every crack means there is a problem with the installation.
For instance, governmental, trade association guidelines and best practices allow for certain hairline cracks, due to the nature of the material. Keep in mind that stucco is basically a thin sheet of concrete attached to the wall. The wall system, be it wood frame or light gauge metal frame, is susceptible to small deflection and bending. Should the bending on the wall occur, the stucco siding may be subjected to bending as well creating stress in the stucco and create unwanted cracks like concrete. And like all concrete it will inherently have some cracks. Latex paint and other elastomeric coatings will hide many such hairline cracks.
Those same guidelines also specify where control joints are to be installed in stucco panels to control the expected cracks. Because stucco behaves so much like concrete, there are supposed to be joints installed in the stucco, just like concrete parking lots. The exact placement of the joints depends on the size of the wall, location of window and door openings and various other factors. Omission of control joints, or improper location can contribute to cracks in the stucco finish.
Traditional hard stucco is applied in three distinct layers, with metal lathe fastened to the wall before any of the stucco is installed. A water resistive barrier is included as well, to manage any moisture that migrates through the stucco (yes, moisture will move through stucco!). How all these components are installed is critical and an error at any phase can result in cracks in the finished product.
Diagnosing the cause of stucco cracks requires experience and should be referred to a competent consultant.