It's Not The Product, It's the Installer.
Upon that visit, the vendor rep. immediately found the reason for the valve not functioning properly. The customers "contractor" (who previously blamed the product) installed the valve upside down and thus the cold and hot water inlets were reversed; which caused the valve to malfunction. The client was very happy to finally know what had been the problem, however, he was very saddened when he was told that the only way to fix it was to remove the newly installed tile, remove and reinstall the valve properly.
The lesson here is: I cannot stress enough the importance of hiring qualified people to install your products. If you do not know of a company, Kitchen Bath Warehouse is happy to provide you with the names of several licensed and insured plumbers. Every product we sell in our store that contains a cartidge is water tested for leaks and functionality prior to leaving the factory. This insures that your product is in perfect working order when you receive it.