This magnet thing might have legs. My SB always drains when powered off. The last wo nights the lid has been left open and I had no power loss in my batteries. I am going to experiment a little more and will post again.
So I was on another site reading about another user experience and discovered something that seemed impossible.
Apparently, this user said you can actually detach the screen when the SB is in full power down mode. Completed shut down and attempted and guess what? User is CORRECT.
Now, maybe I am late to the party with discovering that, but given that knowledge, it would seem this might be one of the bigger reasons we are seeing significant battery drain when fully powered off.
As previous user said, "significant design flaw" seems to be appropriate wording. How else can you detach the screen when it has no power?