I came to edit some of my automations and notice that I can no longer set the state of devices correctly, the GUI shows an error as below:
and when this happens I get a corresponding error in the logs files:
Does anyone have any ideas ?
It is a Z-Wave device as below
Note I am getting this problem on multiple of my Z-Wave switches
OK, I solved this.
It looks like quite a few of my zwave devices have sensors that report as “unavailable” in the GUI - not sure where they came from, guess zwavejs at sometime added them.
Anyway, deleting these unknown sensors/entities then allows me to edit the automation correctly.
Fireplex - thank you for come back and explaining your solution. I did not think to delete Unavailable sensors myself. This has saved me days of troubleshooting!
Glad it helped 
