Hi mrmsharris... I also have a rainbird sst900i and have problems with zone 1 and zone 5. What I found was those two zones are in a separate part of the lawn (almost 2 acres). I dug up the valves and cut the old connections, cleaned the wire and reconnected. I then went to the other zones (another area of the lawn) and found the common line, cut those wires, cleaned and reconnected. That fixed the problem. So there is a problem with the wires I don't think it is the controller. That said, my system has been here for a long time. I bought the house 5 years ago. I have to add more heads to the zones and add one more zone so when I rent the trencher, I am going to replace all the wires. who knows if some goofball didn't put a splice somewhere in the yard.