Visible crew/equipment: When Mammy catches Scarlett trying on a pretty bonnet when she is supposed to be in mourning, when the camera pans wide to show the room, in the mirror on the wall behind Scarlett you can see the shadow of the grip holding the mic above Scarlett.
Revealing mistake: After Frank Kennedy's death, Scarlett is drinking in her bedroom, when she spies Rhett arriving outside her window. She then races to the mirror to brush her hair. She does not actually touch her hair with the brush strokes, probably so as not to disturb her hair, which had been specially styled by hair and makeup staff.
Chosen answer: It looks to me like a bird flying from the tree to the ground. Nothing controversial there and no reason to edit it out.
ChiChi