I rarely had a failure with a keypad QQQ. Most of the damage and/or replacement was from thunderstorms / static discharge and faceplate removal. I would disagree that they were a nightmare. Of course, there were some poorly designed products in the line that had trouble, namely the lighting controls MLCs, but the rest of the products I had decent luck with. JMO
If 4 out of the 6 keypads are indeed dead, I would be one to change out the entire system to another, but we need more information on the components that made up this PHAST system.