Visible crew/equipment: Spade returns to Brigid O'Shaughnessy's apartment and tells her about his meeting with Joel Cairo. Right when he says, "He offered me $5,000 for the black bird," the shadow of the boom mike can be seen above the fireplace. (00:31:55)
Revealing mistake: The edge of Kane's ageing wig protrudes excessively when he meets Susan, and even more so when Jed sends a boy back to him with the Declaration of Principles. When viewed on a large screen, the effect is unmistakable: the entire wigline stands proud around the head.
Suggested correction: I have no idea what you mean by the "wig protruding too far." If you're talking about that grey area on the side of his head, that is nothing more than a shadow that changes shape as his head moves.