All primary inspection agencies shall be responsible for acting as necessary under their contractual commitment with the manufacturer to determine whether alleged failures to conform to the standards may exist in manufactured homes produced under their surveillance and to determine the source of the problems. The DAPIA may be required to examine the designs in question or the quality assurance manual under which the manufactured homes were produced. The IPIA may be required to reexamine the quality control procedures which it has approved to determine if they conform to the quality assurance manual, and the IPIA shall have primary responsibility for inspecting actual units produced and, where necessary, for inspecting units released by the manufacturer. All primary inspection agencies acting with respect to particular manufacturer or plant shall act in close coordination so that all necessary functions are performed effectively and efficiently.