Has anyone had trouble with the display going out on the z4? I have a 2 year old install for a church that has 4 v2 heatpumps with 24 z4 controllers. I have replaced 6 of these controllers with z5's, with 1-2 per refrigerant circuit. I have never had a problem with the z5, and was just wondering if I'm the only one. I always have 12vdc at the wall plate, but just a blank display. The church has a 10 year warranty on parts, but these controllers only come with a 90 day warranty.  We have never had this problem with any other large install, but this is the only one with the z4 controllers. I don't think its an install/wiring issue as this is the only location having this repeated issue.