RBoy
(www.rboyapps.com - Making SmartThings Easy!)
4
Since you’ve tried battery replacement, I’m assuming that you have a C-Wire which is causing the issue when there is an power outage. Try disconnecting the C-Wire and see if works. If not then the thermostat is defective and would explain the issue.
There are lots of Z-Wave thermostats to choose from depending on what feature you’re looking for. For example the GoControl has additional features such as limiting the max and min temperatures. Where as the CT-101 is a Z-Wave Plus, stable but basic thermostat. You can get more details about Z-Wave thermostat models and features on this topic: