Can you have one light in a group?

I had a group set up with two Hue bulbs in it and was using it being switched on / off to trigger a ZWave plug that controlled a third light. I had no problems with the setup at that time.

I have recently moved a few lamps around and now have in this particular room, one Hue bulb and two Z Wave plugs, so rather than change all my automations which rely on group.dining_room_lights turning on / off, I just removed the old bulb from the group leaving me with a single bulb in the group.

Admittedly I upgraded HA to 0.40.1 at the same time, but am now having a few odd side effects:

  • An error in my log telling me “homeassistant.exceptions.NoEntitySpecifiedError: No entity id specified for entity Dining Room”

  • My Z Wave plugs are intermittently switching on an off together as if the Hue bulb has been turned on / off and triggered the automation.

I am struggling to get to the bottom of this and was wondering if it had something to do with only having one light in a group? (I have tried adding the old bulb back in without it actually being in a lamp but still the same problem)