what plugin module is that?
Did you check the logs for any errors?
The plugin module is this one http://www.uk-automation.co.uk/products/Z-Wave-Appliance-plug-by-TKBHome.html
I didn't check the logs for errors, I will report back if I try again. The operation of the module itself seemed to be fine, it was just the light wasn't behaving as expected.
I had an odd similar issue with one Z-wave module that supported load detection. My guess would be that like the Z-wave module, the security light needs constant power to keep its detection circuitry alive. This draw could be telling the module that local power (via Amp draw) is requested.
I am fairly familiar with some of your other projects so will recommend getting a meter and experimenting/testing to see how much draw the light needs. Perhaps there is a way in the zwave-api to turn off certain features like local load switching?
To get around it another way you could use the zwave module to turn off a relay placed between the devices. Wired normally open this would allow you to kill attached devices regardless of any 'leaked-power' they try and pull. Good Luck.
Yes I wondered if it was something like that, basically keeping the light on. I also had a similar thought about relays/switches. Not sure what that would look like though, might not end up looking that elegant.
I have now removed the plugin module, and the light doesn't turn off properly now anyway! I don't know if the plug-in module fried/damaged something in the light. It's no biggie, these lights are going to be replaced anyway, this was just a stop gap until such a time. Maybe I should consider a z-wave PIR module and use a "normal" light on a z-wave switch, then I can have complete control over dimming, security mode, etc.