Plot hole: Shaft's friend has been killed at the beginning of the movie. Bad guys show up at his sister's door for a fake flower delivery, and Shaft kills them. He asks the dying baddie "Who put a contract out on me?", but how does he know? We as audience know there is indeed a contract on Shaft since we've seen the conversation with the mobster, but as far as Shaft knows, all evidence points at Arna being the target, and he even explained the money-related motive a mere minute before.
Revealing mistake: When Shaft fights the bad guys disguised as flower delivery men, both die with their blood packs that explode triggered by visible pyrotechnics - kinda odd to shoot a guy and see literally flames burst out from his chest or back before any blood comes out. (00:48:50)
Continuity mistake: Mr. Kelly pimpslaps Rita as she is grabbing her things, and he walks away to answer the phone. Between shots, the mules on the table have rotated, and in similar fashion the suitcase is also now parallel to the side of the table instead of being at an angle. (00:34:30)
Continuity mistake: When Captain Bollin is questioning Shaft in his office, his hand position between shots is not always consistent. Best example when he asks Shaft about Mascola: he is leaning with his left hand on the top of the file cabinet, but he's shown rubbing his hands together in the following shot. (00:29:40)
Continuity mistake: The mafioso with the rainbow scarf hands his boss a drink, extending his arm. The next shot begins with his arm bent, and the third mafioso acting as barista is also in a position inconsistent with the previous shot. (00:15:00)