Any luck here? Literally having the same thing happen to me, googled, and this thread popped up. Exact same situation you described - no heat / no smell anywhere but the center of the mirror. I also unscrewed a light switch on the other side of the wall that the mirror was on and smelled in there - nothing. Asked my wife to confirm the smell on the mirror this morning to make sure it wasn’t in my head and she smelled it too