Check your log (mono output). If HG is commanding the lights to come on, it should have a line that shows what program is running the command.
Also, you might want to check the modules.xml file and look for the light that's being controlled on to see if it has something in the parameters that you don't expect. I had an instance a while back (early last year I believe) where lights were turning on or off (can't remember which) at 9pm even though I had nothing set up to do so. I looked in the xml file and found a reference to it as I recall. After playing around for a while, the interface showed the 9pm line out of nowhere. I deleted that section and things worked as expected again. I have no idea what happened, but it was definitely strange.