It's just a game glitch and it means nothing. Don't worry about it. You will notice that if something does not have a shield the shield power button will always be on.

Yea I noticed whether it was on or off it didn't draw any more or less power so not really consequential but just annoying.

I did get it to shut off eventually by installing some spotlights (which was what that device group was before) and then assigning them to that group again. Now it stays off.