I dont know why this would happen but there is a way that should fix it. See this thread:
GE switches have a parameter that can be set to invert the switch if needed. The default device type for z-wave switched does not let you change the parameter but this custom type does.
In the SmartThings App - go to the device - select the gear on the upper right side. At the bottom you will see “LED indicator” tap here… you can select in which state you want the LED indicator light to illuminate.
I’m having the same issue. I’ve got like 10 of these switches in my house and only one of them changed. I looked at the log and I see one entry that’s out of the ordinary.