Prolbems with Speakercraft MCZ 88 whole house systems

Can anyone make some suggestions to me on what else to try? We have had a system installed with the main receiver being a Speakercraft MCZ88 their control key pads and speakers. It was installed by a guy I know who has done many of these in the past with the exact same units used. We are now waiting on the replacement of the third MCZ88 in two months. The first one died after about two weeks and we were told Speakercraft said it had a bunch of blown fuses inside. The second and third units just stopped having sound #2 lasted about 10 days and #3 lasted about 3-4 days. The installer has us with sound using a temporary back up Harmon Kardon but not being able to change cable stations without going into the electronics closet and just pure frustration is killing us. They have run many test ie OHM rating on each speaker, a speaker, keypad and wire continuity test as well as each key pad. We have a APC1500 battery back up and surge protector and had a electrician install a dedicated power line to the closet. The closet gets warm but not hot and is well ventilated. What else can we try, test or check? We have been using a ipod most of the time for a source and the last time it worked until I turned it off then the next morning the sound was dead. I am going nuts any help would be really appreciated. Thank you in advance. PGG